CA2350453C - Method and apparatus for removing water from well-bore of gas wells to permit efficient production of gas - Google Patents

Abstract

Method and apparatus for removing water from a gas well to permit efficient production of gas while protecting formation from introduced pressures. The apparatus comprises a check valve that seals the casing from production zone when hydrostatic pressure of water from production accumulates in casing above production perforations and checkvalue exceeds formation pressure. When the casing is sealed, a compressor pressurizes gas into the casing but not an exhaust conduit, the top of the casing being sealed around the exhaust conduit, permitting communication between the conduit and a suitable destination, such as via liquid separators on into sale pipeline. Accumulated water is caused to flow into the bottom of the exhaust conduit and out at surface to collection. When pressure within the sealed casing to the top end of exhaust conduit is equalized, the checkvalve opens and regular production can resume.

Description

METHOD AND APPARATUS FOR REMOVING WATER FROM WELL-BORE
OF GAS WELLS TO PERMIT EFFICIENT PRODUCTION OF GAS
FIELD OF INVENTION
This invention relates to an improved method and apparatus for the removal of water from the ~n~ell-bore of gas wells so as to reduce the hydro static head associated with the produced water and to thus unload the 'n~ell and permit more efficient production of gas.
BACKGROUND OF THE INVENTION
Numer ous gas wells in Alberta, Canada, and throughout the world, produce a minimum of natural gas because of pr oblems associated ~~ith water produced with the gas, ~~hich accumulates at bottom-hole, and by vir tue of its ~~eight provides a hydrostatic back pressure which partially or entirely defeats the ability of formation gas pressure to move well gas to the surface for collection.
There are a number of methods in use to remove water from the well-bore of a pr oducing gas well when the column height of water in the bore produces a hydrostatic pressure greater than the pressure of the gas from formation sufficient to impair production.
The gas in those situations has typically been produced out of a smaller

2~ diameter tubing string inserted into the well because the smaller cross-section of the tubing produces higher velocities of gas floe at formation pressures ~n~hich it is hoped will carry the water out of the well-bore during production and thus "unload" the well.
As a reference, the article "A Practical Approach to Removing Gas V~~ell Liquids" ~-vritten by E.J. Hutlas and W.R. Cranberry (published August 197? in Jo1iT31Cil of Petroleum Technology) discusses the history of methods of removing un~n~anted accumulations of liquids from gas wells. 'the article states that the best methods for removing liquid from producing gas wells are pumping units, (for shallow fields having very low pressure), liquid diverters, intermitters and gas lifts ~ (for deeper higher-pressure fields), and inserted tubing strings for wells where severe formation damage could result from stopping operations (e.g. well shock).
United States Patent No. 4,265,312 to Theirs, METHOD FOR DEVELOPING
WATER WELLS, issued May 5, 1981, per tams to a method of developing a water ~n>ell, but is instructive in that it deals ~n~ith the introduction of a gas-lift eater pump into a well-bore, the pump's action being provided by introduction from surface of high-pressure gas (air, in that case) in an inner tube deployed such that its bottom end is above the bottom end of an outer tube in ~~hich the inner tube is centered, and the bottom of both of which tubes are deploy>ed submersed in the ~n~ell-bore's accumulated water. The pressured gas escapes from the bottom of the inner tube and is collected and exits the well-bore, r ising up through the annulus between the pressurized tubing and the second, outer tube, taking ~>ith it entrained ~~~ater from the wellbore (within which the tubes were deployed).
In the Theirs patent, the purpose was to provide a gas-lift pumping means with some agitation at the well-bore's bottom end to remove settled solids and improve water flo«~ within a eater well. The apparatus is a good example of a form of gas-lift pump (concentrically deployed tubing strings, providing pressurized gas from surface to the inner tube, permitting gas and entrained liquids to exit using the 2~ annulus between inner and outer tube as a discharge path).
There are two related prior art downhole pump systems, US Patent No.

3,894,583 and US Patent No. 3,894,814 to Morgan, both issued July 15, 1975, titled ARTIFICAL LIFT FOR OIL WELLS, ~1'111c11 describe a two-chamber do~~n-hole pump apparatus to be removably inserted into an oil well's casing to pump oil from an oil well where production pressure is insufficient to provide lift to surface.
Morgan's '583 patent describes an apparatus and system where the well's casing is isolated by a packing from the production zone and from the pump at bottom-hole to provide a storage tank for compressed air, an accumulator below the packing to collect oil from formation via a check valve which is vented to surface, said vent line being periodically pressurized by connecting tubing and valves to the casing's stored pressurized air to force the collected of from the accumulator up a secondary tubing string to surface. A piston, pig or s~neab is deployed below the oil in the production tubing string. The vent/pressure tubing is deployed adjacent/concentrically to said production tubing. Crossover conduits between production tubing/venting tubing are used to s~n~itch annulus mid-bore. An electric switch/ball float is deployed in the log-~~er well-bore to sense the accumulator's state 1 ~ (full or not), and to energize an air pump top-hole and electrically switched ~~al~~es to pressurize the ~~ent tubing.
Morgan's '81=~ patent describes and claims the same system and apparatus, absent the use of the upper casing as a pressure tank and requiring an electrically actuated 3-way ~~al~~e and dog-~~n-hole sensor.
Morgan's '583 patent also describes an embodiment ~n~here the accumulator means is formed by a chamber comprised of the ~~ell's casing belo~~ the packer isolating the upper casing's compressed air storage area from production, and also 2~ belo~~ a second packer below the perforations in the casing to formation, with a check val~~e from the thereby isolated production zone of tile casing into the accumulator chamber below said second packer, said production and vent tubing extending in a sealed way through both packers and into the accumulator zone.

In US Patent No. 3,797,968 to Elfarr, issued March 19,1974 APPARATUS FOR
FLOWING LIQUID FROM A WELL, describes a downhole siphon pump apparatus for producing oil from an oil well where formation pressure is insufficient to move oil from bottom-hole to surface, powered by compressed gas from surface. The ~ Elfarr system is comprised of two concentrically deployed tubing stings inserted within the well's casing. The inner tubing string for its length to near bottom carries compressed gas from surface. The annulus between the two tubing strings carries oil from the bottom-hole pump to surface. Near the bottom, the conduits cross-over via cross-over passages in a fitting. At various heights in the production annulus, check valves are deployed to permit upward-only flow of oil. At bottom, a check valve permits oil from the formation in the casing to enter the outer conduit and accumulate in the tubing string's outer annulus. A check valve in the bottom of the inner tubing string, below cross-over and above the lower check valve is deployed permitting oil to floe upward only into the production passage~n~ay for pumping.
1 ~ The ilmer tubing at surface can be pressurized, causing the pressure differential across the check ~~al~~es at bottom to (a) close communication between the t~-~~o tubing strings and the casing; and (b) Open C0111II1unlCatlon between 11111er and outer conduits, permitting and causing the accumulated captured oil to flow up~n~ard to~n~ard the surface. The formation is thus not exposed to higher than bottom-hole ambient pressure. The check ~~al~~es in the outer production annulus and the system can be cleared by removal of the inner tubing string, which is for most of its length (from surface to cross-over) used ol~ly to carry pressurized gas from the surface.
There is thus formed a pump ~~ith two chambers deployed up-hole, formed of concentric-tubing strings, cross-over fittings, and check val~~es, with the removable inner str ing sitting on nipples and seats on tile inner surface of the outer tubing string, for pumping oil from wells using introduced pressurized gas from surface. The pump was designed to move oil to surface in an oil well to enhance production, but it is complex, small-diameter, and requires specialty fittings, seats and nipples, and it has a large number of complex and special-purpose ~~al~~es. It a would interfere significantly with free gas-flow, and while it operates on pressure differentials (a siphon-like function), it is for the speci:Eic purpose of pumping oil to surface.
United States Patent No. 4,509,599 to Chenoweth et al, GAS WELL LIQUID
REMOVAL SYSTEM AND PROCESS, issued April 9, 1985, describes a system and apparatus for dewatering a gas well which, at the well-bore's bottom end has collected sufficient fluid (water, for example) that the bottom-hole pressure (adjacent the production from formation to casing) is insufficient to independently transport gas from formation to surface (through, it is assumed, a conduit or tubing string secondary to the casing's cross-section).
Chenoweth's invention pro~~ides for the division of the casing's annulus into 1 ~ tmo independent conduits (typically, a tubing string and the casing/tubing annulus), with a compressor at surface producing lo~n~er pressure ~~ithin one of the conduits sufficient that production pressure (from formation) at bottom-hole propels gas-fluid mixture to surface through that low-pressure conduit, permitting gas alone to flow through the other conduit (once the o~~er-pressure situation has been remedied by remo~~al of sufficient fluid from the well's bottom). There is also provided a means of heating the top segment of the mixed fluid-gas-carr~~ing conduit to a~~oid precipitation of paraffin.
It is a necessary part of the Chenoweth in~~ention that both conduits 2~ communicate with formation throughout the process claimed. It is also provided that a lowered pressure (partial ~~acuum) is applied, at surface, which Can be difficult, and which might damage the well's production interface. It does not contemplate any need to segregate production zones from the method or apparatus for dewatering the well. It is a "closed" systelll 111 that all matter exhausted from the s ~~ellbore is (once liquids are separated) inserted into the gas collection system to the sales line.
The discussion in the prior art cited in the Chenoweth specification discloses the insertion of highly pressurized gas into a ~n~ell-bore to cause the e~~acuation of gas and liquid from well-bottom through a second "siphon tube" string to "unload"
a gas well, as well as methods involving gas-lift valves, downhole mechanical pumps, differential gas intermitter systems, and the like, and claims to overcome the difficulties inherent in those systems. Of particular interest here is the mention of insertion of high pressure gas to "blow" liquid-gas mixtures up a siphon tube depended within the well's casing, as a variant to reduction of pressure from collection system pressure ranges to lo~n~er, atmospheric pressure ranges, in order to exhaust gas through the SIphOI1 tube at hlgh ell0ugh ~'elOCltleS to unload the problematic well.
1~
The cure in the objects of the Chenoweth '599 patent for damage potential frOlll hlghh' pleSSUrIZIIIg the CaSlIlg (and production fl7rmatlOn) 1S to significantl~~
reduce the pressure through the siphon tubing, thus permitting formation pressures to be the highest pressures in the system (and thus eliminating formation damage potentials caused by insertion of high pressure gas from surface into casing, which can "drive" entrapped liquids and solids at bottom-hole in the well-bore back through the casing perforations into formation).
United States Patent No. 4,437,514 to Canalizo DEWATERING APPARATUS, 2~ issued March 20,1984, discloses a ~~al~~e-set comprised of two valves, one permitting liquid-only fluid flow from casing-tubing annulus into tubing, the other, higher, ~~alve permitting communication from casing-tubing annulus of gas or liquid into the tubing. The valve-set is put at the lower end of a tubing string, and may be actuated automatically or from surface.
G

During operation, when the ~n~ell-bore begins to fill ~n~ith ~n~ater from production, the water rises within the casing-tubing annulus, and when its hydrostatic pressure is sufficient to open the lo~~er valve, water is made to enter the tubing string. When the tubing string is filled to a desired level, the second, higher, valve is opened, and the tubing, being open to atmosphere at surface, is over pressured by pressure of produced gas and liquids, ~n~111c11 thus enter the bottom of the tubing string and cause a gas bubble to enter and to evacuate water and gas to surface, optionally ~~ith the use of a pig or plunger between the gas and trapped ~n~ater. This may be referred to as a gas-lift intermitter.
When suitably evacuated, the pressure in the casing-tubing annulus ~~ill have dropped, it being sealed at surface with collection tubing with a third check (one-way out) valve, which causes the second, higher valve to close, shutting off produced pressure to the tubing.
1~
There is no need to insert additional pressure to the casing-tubing annulus, nor is any method disclosed. There is no seal of the well-bore above production, as there is no intr oduced pressure to damage the pr oducing formation. A problem which the'~1-1 system will encounter in deep wells is th~lt the longer length tubing introduces more chances of the equipment binding in the tubing string.
United States Patent No. x,226,28-1 to Evans, GAS WELL DEWATERING
METHOD AND SYSTEM, issued October 7, 1980, provides for a closed system of pipes and valves operable via a timer, which permits casing pressure to den-eater a 2~ gas well b5~ blowing produced gas d0~-1'11 aI1 lllSerted tubing string using pipeline or formation pressure, so that entrained water with produced gas is blo«~n back up the casing/tubing annulus directly 111t0 a COn~'elltlOnal pTOduCtlon COlleCtloll S~'SteI21 («~hich typically includes a normal gas flo~n~ line and liquid separator means), in order not to waste pr oduced gas in the dewater ing pr ocess.
JO

Other~~ise, the Evans invention shoes no increase in casing pressure, nor any method of protecting the formation, the inventi~~e step being the closed piping and valve system with timer. Energy is provided again from pipeline or production pressure to the lift mechanism.
Canadian Patent No. 848,766 to Kelley and Kelley, LIQUID CONTROL FOR
GAS WELLS, issued August 11, 1970, discloses an apparatus to control the liquid depth in gas and oil wells. This invention is comprised of a positive action liquid/gas separator within a well-bore, a tubing string within the well-bore connected to the separator, a gas lift ~~alve connected to the tubing string and responsi~~e to predetermined pressure (supplying gas under pressure from the well-bore to the tubing string so it lifts liquid through the tubing string to the surface), and a free piston member (or pig or swab) retained within the tubing string for movement between the gas lift val~~e and the surface belov,~ the column of liquid (to assist the gas lift in dri~~ing the column of liquid from the well b5~
segregating the neater abo~~e the lift gas).
Canadian Patent No. 890,226 to KelleS~ and Kelley, APPARATUS FOR
REMOVING LIQUID GAS FROM AND OIL WELLS, issued January 11, 1972, discloses an apparatus for the remo~~al of liquid from gas and oil ~~ells.
This in~~ention is similar to Canadian Patent No 8-18,766 absent the liquid-gas separator but with the addition of a self-lubricating free piston member (to replace the free piston member). The in~~ention shows an intermitter gas lift ~n~ith a free piston. The free piston is disposed in the tubing string and retained by a bottom stop and 2~ catcher apparatus, and is lifted b5~ introduced gas from formation below the column of liquid to distribute the pressure of gas admitted to the tubing string b5~
the gas lift de~~ice across the bottom of the column of liquid and to avoid the gas dissolving in the liquid as it is lifted to lo~n~er pressure regions. ThlS 111~'elltloll pro~~ides automatically regulated 111terI111ttellt flog-v through the tubing string without manual control or c~~cle timers. This in~~ention and Canadian Patent No. 848,766 require s relatively high inherent (not introduced) differential gas pressures to operate r eliably.
United States Patent No. 5,339,905 to Dowker, GAS INJECTION
DEWATERING PROCESS AND APPARATUS, filed November 1992, discloses a gas injection dewatering process and apparatus. In this invention a conduit is provided in a watered-in well in the form of tubing of smaller diameter than the well-bore or cased bore to conduct ~n~ater from the bottom of said well-bore to the surface, said conduit including a check check-valve such that «Then water flows up~n~ard, it cannot then reflux backward.
Periodically, a volume of dried, pressurized natural gas is injected into the lower end of the conduit from an adjacent gas line from surface and which injected gas is then allowed to expand, thereby forcing a slug or column of water upward 1 ~ through the conduit to~n~ard the upper end. This is a typical "gas lift"
method.
This "pulse" of induced gas is repeated, being pumped periodically do«~n the secondary conduit through the «~elI-bore or casing through that conduit, and then being alto«~ed to expand «~ithin the production tubing conduit in or der to cause a pulse of increased pressure within the production conduit «~111c11 1S Illeallt t0 Cause the ~s~ater into «~hich that conduit is depended to be forced to surface.
In one embodiment, there ar a t«~o conduits deployed essentially in parallel down the ~n~ell-bore's length from surface to below water, with one being an exhaust 2~ conduit and the other being a delivery system for the pressurized dehydrated natural gas, ~n~here the said dehydrated natural gas is injected into the body of the exhaust conduit, thus causing a "bubble" of expanding gas to flow upwardly ~n~lthlll the said exhaust conduit, decreasing pressure within the exhaust conduit and thus pulling «~ater up the exhaust conduit coupled ~s~ith pulses of expanding gas.

There are a number of difficulties with this system, chief amongst them being that by pressurizing the well-bore to force water up the conduit this method also can cause the pressure within the formation ~n~ith which it is in communication to increase, and incidentally causing the eater (and any included matter) accumulated S lI1 the well-bore to be forced back into the formation, together ~~ith any sand or other substance in the well's bore at bottom-hole near the casing, and thus "reloading" and potentially damaging the formation, rather than evacuating the accumulated water at bottom hole.
Additionally, this invention requires special equipment to provide dehydrated natural gas under pressure, and requires the deployment of specialized dual/parallel tubing and injector mechanisms, thus being more costly than desired.
United States Patent No. 4,823,880 to Klatt, GASWELL DEHYDRATOR
1 ~ VALVE, filed September 1988, discloses a gas «~ell dehydrator valve. This invention deals with the particular situation of t~vo contiguous producing gas zones within one well-bore, both being produced simultaneously, the tower one through a tubing dependent past a segregation packer in the «~ell-pore between the t«~o zones.
Then the upper producing zone produces sufficient eater such that the h~~drostatic pressure caused by that eater's accumulation above the segregation packer within the «~ell-bore overloads the production from that upper zone, this invention's sa~stem provides for a special valve within the packer to allow communication of the gas under higher pressure from the lower formation to be introduced to the annulus bet«~een the inner conduit and the well's casing, where the upper production is 2~ done and ~n~here there is no~n~ ~n~ater accumulated, in order to use that introduced gas pressure to essentially "pump" or "blow" said accumulated water up that annulus to surface, reducing the hydrostatic pressure and unloading the upper formation, allo~~~ing production from the upper reservoir to resume under natural pressure (when the specialized packer-valve is reset).
JO

This invention has a number of particular deficiencies, notably: the requirement for t~n~o contiguous production zones, the lo~~er zone not accumulating water from formation (i.e. maintaining its natural pressurization sufficient to clear the accumulated water in the upper zone); the requirement for specialized and complex valve and actuation devices at the segregation packer and the packer itself, together with difficulties inherent in properly locating and sealing those apparatus properly in the well-bore.
United States Patent No. 4,171,016 to Kempton, WATER REMOVAL SYSTEM
FOR GAS WELLS, filed February 1978, discloses a water removal system for gas wells. This invention involves a set of concentrically deposed tubes with a specialized injector at the bOttOIl1 elld ~1'lthlll a 'fell-bOTe, depending 1I1t0 water at the well-bore's bottom. Pressurized water is pumped do~n~n the annulus between the inner tube's outer ~,~all and the outer tube's inner «~a11, and is injected at bOttOIn 1 ~ ups-vardly into the inner tube's annulus, causing said water to jet under significant pressure up the inner tube, ~n~hich in turn causes the pressure «~ithin the inner tube to drop somewhat from the pressure within the formation, and thus causing the water within the well-bore to flo«~ or be thus pumped to surface. This is a do«-n-hole 1I11eCt10I1 Or jet pump.
There are a number of difficulties ~-~~ith this system and method, chief among those being the requirement to pump Iarge volumes of water at relatively high pressures into the well-bore near the formation in order to cause sufficient jet-pumping pressure differentials to evacuate the water from near to the formation.
2~ Additionally, if the injector becomes damaged or clogged, this system will result in additional volumes of water being introduced to the production zone of the «~ell under high pressure, thus potentially seriously damaging that well's future ability to produce gas.

United States Patent No. 4,596,516 to Scott et al, GAS LIFT APPARATUS
HAVING CONDITION RESPONSIVE GAS INLET VALVE, issued June 24, 1986, discloses a gas lift where a siphon tube is deployed ~~ithin the well's casing, and near the bottom end of the siphon tube is a valve, operable from surface (or alternatively, responsive to the differential between hydrostatic pressure of a column of water within said annulus and the pressure within the siphon tubing), ~~hich, ~~hen opened, permits communication from the casing's annulus outside of the siphon tubing with the inter for of the siphon tubing.
The valve structure is sealed to the casing (belo~n~ the communications openings) by a set of two packings, situated above the perforations from formation to the casing's annulus. The seals or packings are provided with a pipe which (full-time) communicates from formation to the casing's annulus, said pipe extending ~~ithin said annulus upward from the packing to abo~=e the operative parts of said 1 ~ valve.
~~l~hen the wellbore including the casing annulus and the tubing string (siphon) are filled with produced water, and it seems desirable to evacuate said ~-eater, the valve within the tubing is opened, permitting produced gas from for oration to enter said valve above the packing seals, and to enter the siphon tubing, causing a bubble of produced gas to "burp" up the tubing, and evacuate «~ater therefrom to surface (~1'lth the optional assistance of a piston-like "pig" which travels above the gas slug but belo~~ the moved liquid to surface, where the liquid is drained off and the pig is permitted to descend the tubing to bottom).
There is pr ovided no means of fully sealing the wellbore just above casing perforation to protect the production formation during pressurizing of the well.
Formation pressure, ~n~hen introduced through the novel valve/seal means, is sufficient to provide gas-lift to evacuate water without adding or inserting pressure to casing.

This, then, is a typical downhole valve system of evacuating ~n~ater from a producing gas well's bore using a second tubing string and production pressures and gases to provide necessary lift.
J
Objects of the Invention It is an object of this invention to overcome or mitigate as many of the difficulties apparent in the prior art as is workable.
SUMMARY OF THE INVENTION
This invention is a system and apparatus for the removal of water from a gas «~ell.
1~
The present in~~ention o~~ercomes or mitigates some shortfalls in the prior art, chiefly those which concern potential damage to producing formation or to the w~ell-bore and casing from injected pressurized fluid or gas to power pump or lift devices, the insertion of pressure into the «~ell-bore which could communicate either directl~~
or ~~ia pressure conve~~ed through fluid and gas in the ~;vell-bore to the production formation, or similar problems. As well, the present in~~ention provides an efficient system of ciewatering and thus unloading a watered-in gas ~~ell with locally obtained pressurized gas using facilities, materials and equipment ~~hich are conventionallST available and easy to operate either manually or automaticall~~ in the 2~ field.
In accordance ~n~ith a broad aspect of the present invention, there is provided an assembly for pr oduction of gas from a do~~n-hole gas-producing formation to surface through a well bore lined ~Vltll CdS111g lla~'lllg Ope11111gS thlOUgh ~1'hlcll gaS
.O0 CaI1 paSS frOIn the fOrlnat1011 IIltO the casing alld the assembly being capable of perivdicahy clearing of accumulated liquids whex< the pressure of produced gas is insufficient to overcome hydrostatic pressure of the accumulated liquids, the assembly carnprising: a tubing stzix~g extending from surface through the casing and havixtg a lower open end positioned below a. point at which the hydrostatic pressure of accumulated liquids exceeds the formation pressure of produced gas, the tubing string having a bore sealed from fluid flow communication with the casing except through the lower open end; a check valve positioned and sealed to the casing above the openings and below the lower open end of the tubing string, the check valve permitting flow of fluids from formation through the openings to the lower end of the tubing string, but restricting reverse flow therethrough; and a means for introducing gas from a source of pressurized gas at surface to either the casing or the tubing sizing to create a pressure in excess of the hydrostatic pressure exerted by the column of accumulated liquids above the accumulated liquids to push the accumulated liquids from botta~an hole up through the other of the casing oz' the tubing string to surface and out of said well bore.
A, means for collecting fluids passing from the casing at surface; a means for collecting fluids passing froxx< the tubing string at surface may be provided.
In accordance with another broad aspect of the present invention, there is provided a method of unloading accumulated liquids from a well bore to a level sufficient to permit gas to be produced from. the well bore, using formation pressure, the well bore being lined with casing and haviztg openings in the casing to permit produced gas to pass from a formation into the casing, the meEllod comprising:
providing an assembly including a tubing string extending from surface through the casing and having a lower open end positioned below a point at which the hydrostatic pressure of the accuixlulated liquids exceeds the pressure of produced gas, the Tubing stnizlg having a bore sealed from fluid flow communicattioxt with the casing except through the lower open end; a check valve sealed to the casing above the openings and below the lower open end of the iubirlg string, the check valve permitting upward flow of fluids from the openings or perforations to the lower open end of the tubing string, but restricting the reverse flow therethrough;
and a means for introducing gas ~rox~n a source of pressurized gas at surface to either the casing or the tubing string; closing the check valve; introdudng gas from surface to either the casing or the tubing string to create pressure in excess of the hydrostatic pressure excited by the column of accumulated liquids above the accumulated liquids to push the accumulated liquids from bottom-hole up through the other of the casing or the tubing string to surface and out of said well bore; and stopping introduction of gas from surface to permit the well bore to return to production of gas frozxl the formation.
A means for collecting fluids passing from the casing at surface; a means for collecting fluids passing frozx~ the tubing string at surface may be provided.
The casing lines the well bore, as is known and can be standard casing or any other well bore liner. The well bore can be vertical or horizontal and can be the main well bore or laterals kicked off from a ~x~,n boxe hole. Where the well bore services more than one production zone, has a large internal volume or includes numerous lateral well bores, packers can be used to isolate areas into which gas is introduced to apply pressure above accumulated liquids.
In some situations, such as in a dangerous or sour gas well, or other regulated wells, or where the integrity of the casing is suspect, production may be through an internal conduit or tubing string depended or placed within the said well's original casing. The internal conduit extends downward from surface to a packer above the production formation perforations, the annulus between the casing and the internal conduit being filled with an essentially inert fluid or other substance to protect the adjacent environment from leaks in the well's casir5g. In such cases, the internal conduit would be considered for the purposes of this invention to be the "casing" as described in this disclosure.
The openings in the casing will generally be perforations formed through the casing and cement behind the casing, but can also be other arrangements for permitting gas to flow from the formation into the casing such as, for example, a slotted liner or screen or open hole.
The tubing string can be an existing production or production-enhancement S tubing string or a string run in for the purpose of unloading accumulated water from the well. As such, the tubing can be of any desired diameter, provided fluid flow through the casing about the tubing string and through the tubing string is significantly restricted. The tubing used in the tubing string must be rigid enough so that it will not collapse due to the pressure differentials Which will be present on either side of its walls.
In conventional production wells, tubing string diameters can be of Various sizes and still be used in this invention. Typical diameters are 1/2", 3/4", 1", 1 1/4", 1 1/2", etc. The only requirement to operate this invention is that the tubing string's 1 ~ bore (if it is used as the exhaust conduit) has to be of a size that the liquids being removed do not flow down past the gas flowing up tile conduit (for example, 3 1/2" outside diameter tubing is too large if installed in a 4" inside diameter casing, as the compressed gas bubbles through the liquid, the liquid flows down past the gas, and in both instances the liquid is not produced to surface to unload the well).
The pr eS211t 1I1~'elltlOn ~1'lll ~1'Or k ~1'lth 1 / ~" t0 2" tubing installed lI1 a 4 1 / 2"
casing. Generally', it is preferred to use the tubing which is already present in most producing gas ~n'ells susceptible to becoming overloaded with ~n'ater. In cases where the tubing was too large, the present invention generally works if the roles of the 2~ t~n'o conduits are reversed.
Since the level of accumulated liquids Fill be brought do~n'n onh' to the level of the lower open end of the tubing string, the lower open end of the tubing string must be positioned below a point at which the h~'drostatic pressure of the accumulated liquids exceeds the pressure produced gas. Preferably, the lower end of the tubing string is positioned closely above the openings so that a maximum amount of accumulated liquids can be uWoaded in each operation.
The bore of the tubing string can be sealed from communication with the casing by various configurations. One useful configuration is a seal positioned in the annulus bet~n~een the casing inner wall and the exterior surface of the tubing string at the well head.
The check valve can be mounted permanently or temporarily within the casing. The check valve should be of type suitable for the nature of the ~~ell bore and casing. For example, in a vertical cased «~ell, a check valve can be a ball-anc-1-seat mechanism well known in the art, while in a horizontal well, the check valve can be a sprung flapper valve or similar mechanism.
1 ~ The check valve can be installed either by ~~~ireline or can be attached to the lo~n~er end of the introduced tubing string, depending upon «~hich conduit is acting as the 'casing'. If the tubing (which is acting as the casing, referred to as the "casing/ tubing") has a packer isolating the casing/ tubing from the «~ell's annulus, the check valve can be installed with conventional wire-line equipment and techniques, and set at the lo~s~est point in the casing/ tubing (~n~hich is the acting casing) by setting the check valve at the to«~est connection or bottom end in the casing/tubing. The (typically, coiled) inserted second tubing string 'would then be "landed" as close to the check valve as practical, but above the check valve which had been previously installed by wire-line within the casing/tubing at its to«~est ?J COI111eCt1o11, abo~Te its bottom, and below the inserted tubing string.
In s«~eet wells, it is generally IlOt necessary to pack-off or isolate the annulus from the casing/tubing by a packer, and in those «~ells, coiled tubing is used to conduct accumulated water from the well-bore to the surface, the coiled tubing carrying with it as an installed piece at its bottom, an assemble COTISIStIIIg of a landing cone attached to the bottom of the check valve, ~n~hich in turn is attached to a slotted sleeve or similar fitting (to permit communication between the interior of the coiled tubing and the tubing-to-casing annulus through the slots, above the check valve) ~n~hich is in turn attached to the lower end of the coiled tubing; a conventional slip-stop removable packer/seal (ordinarily used to seal the annulus between a fitting on the coil tubing's bottom end's circumference and the casing/tubing within which the coiled tubing is sought to be sealed) is first installed in the casing/tubing above the openings to the production formation, and the coiled tubing with its bottom assembly is lo~~ered until the weight of the coiled tubing and its assembly rests, pressing its bottom-most landing cone into the slip stop, causing a secure seal of the casing/tubing annulus to the check valve, isolating (when the check valve is closed) the tv~~o conduits (coiled tubing's bore plus casing/tubing-to-coil tubing annulus) from the production openings.
1 ~ The wire-line and coiled tubing installers are equipped ~~ith counters which indicate the length of wire or tubing inserted into any well, which indicates the depth t0 ~1'I11CI1 tile ~Nlre-I111e OT tubing has been lo~n~ered. Those counters are generally sufficiently accurate for placement of the check valve above the openings to formation. If the check valve is lowered belo~n~ those open lugs, the well-bore will llOt hold a test pressurization, in which case the check valve should be moved up (usually not more than a meter or so at a time), and retried.
If the seal of the check valve to the casing/tubing is effected by lowering the coiled tubing to rest on a slip stop packer, for example, care should be taken in the 2~ temperature of the pressurized gas ~n~hich is inserted into the coiled tubing's bore to unload the well, because it has been found that insertion of chilled air (from very cold surface conditions, for example) may cause the coiled tubing to contract longitudinally enough to lift the check valve and seat assembly at its bottom off the slip stop, and to thus permit communication bet«~een the Slph011 all allgel11e11t ~s 07/24/01 TUE 10:49 FAX 4032857219 Bennett Jones f~]002 above the check valve and the openings below the check valve, thus defeating the purpose of the invention.
The means of collecting fluids passing from the casing and the tubing string at surface can be a system of conduits, seals and valves and preferably includes a gas collection system including gas/liquid separators, compressors and/or containment vessels as is known in the art.
The seals between the two conduits (for example, coiled tubing inserted into a cased well) are usually accomplished using conventional coiled tubing hangers, an example of which is produced by Select Energy Systems, Inc. of Calgary, Alberta. Such hanger systems provide a composite bag through which the tubing is led, and which when compressed forms a very tight seal between the hanger s body and the tubing's exterior surface.
The means for introducing gas preferably includes conduits, seals and valves from the source of pressurized gas. In one embodiment, the source of pressurized gas is a high pressure pr oducing gas well. Xn another embodiment, the source of pressurized gas is a compressor connected to the well head by a conduit. In that case, a valve is preferably provided to permit closing off the conduit to the compressor ox other source of pressurized gas,. It will be apparent to those skilled in the art the compressor should preferably be automatically operable without requiring attention or priming. It Xs desirable that the compressor be capable of extended unattended stop-and-start operation. One type of suitable compressor is very similar to the low to moderate volume but moderate to high pressure output requirements met by compressors used in filling scuba-diving tanks. The higher the volume capacity of the compressor the faster the water is evacuated. The compressor can also be of a, type mounted on a truck ar large vehicle. Where there is a plurality of production wells closely positioned, there can be one permanent or semi-permanent compressor or source of high pressure gas placed to service all of these wells.
The pressurized gas should preferably remain in a gaseous state at the S pressures to be used. As an example, the introduced gas should not be something like pure propane, which in most circumstances at the pressures required, would be compressed into its liquid, on-gaseous state. Suitable gases for introduction are, for example, surface air or compressed natural gas from the collection pipeline at the well head or produced at a nearby ~n~elI, or nitrogen or other inert gas ~~here chemical reaction might be problematic.
Where the well is producing s~n~eet gas at low pressures, it has been preferred to use air from atmosphere through a compressor as the pressurized fluid in the present ln~'e11t10I1. ~-l~here a well is near a source of natural gas under pressure 1 ~ higher than that requir ed to unload the «~ell and in sufficient volumes, such as a nearby producing «~ell or pipeline, those sources can be used as the surface source of pressurized gas for insertion. 'l~here a well is near to a source of natural gas of sufficient volume but insufficient pressure to be utilized «~ithout compression, compression may be used ~~ith such a gas source.
Ideally, the «~ater produced by the unloading process will be produced into the collection system of separators and sales lines, and carried away from the ~~~ell-site for proper disposal. The compressor used should be large enough to provide adequate volumes of pressurized gas in the required pressure ranges to pr oduce the 2~ accumulated liquids within a reasonable period of time. 'Those types of compressors will be apparent to one skilled in the art. Generally, the less time spent unloading, the more time spent producing, the better.
It is to be understood that the pressure-containing capacity of ~s>ell C0121p011entS SLICK as Well-heads, conduit, piping, joints, packers, fittings, zo compressors, valves, and the like, will have to be sufficiently higher than the pressures encountered during the operation of the system. It is also to be understood that all components of the assembly according to the present invention, must be suitable for use in ~nrell bore conditions, which may be corrosive, etc.
The pressurized gas can be introduced to either the casing or to the tubing string to act on the accumulated liquids. In a preferred embodiment, the gas is introduced into the casing causing liquids to be forced up through the tubing string to surface. This is preferred where the casing is large diameter and the tubing is of relatively small diameter. It is generall~~ preferred to produce pressured gas into the conduit with the smaller cross-section, and to exhaust the liquids from the conduit with the larger cross-section.
The check valve can be closed, in one embodiment, when hydrostatic 1~ pressure caused by the accumulation of water from the production zone in the bottom of the casing above the check valve exceeds the pressure from the formation.
In another embodiment, the check ~~al~~e is forced to close by introducing gas from surface to increase the pressure abo~~e the check val~~e.
The introduction of gas from surface to force liquid out of the ~n~ell can be initiated when it is determined that the check valve is closed, as will be indicated by observing the flo~n~ or produced gas from the well. When the floe of produced gas ceases, the check ~~alve is assumed to be closed. Alternatively, tile llltrOduCtloll Of gas from surface can be initiated on a regular basis by use, for example, of a timer.

Prior to introduction of gas, the casing will be sealed to prevent escape of introduced gas and produced fluids, in order to utilize the pressure differentials, except through the conduit being used to exhaust the accumulated fluids.

The introduction of gas fxoxn surface cax~ be continued until the introduced gas beo ns to be expelled after the accumulated liquids are exhausted, or for a selected period of time, regardless of whether water continues to be evacuated.
There are other situatxoxis and well configuxatlons which those skilled in fine art would consider to be equivalent to "casiz~gs" or "conduits" or "tubing strings", or to "bores' or "surface" or "collection systems" or "gas", "fluid", "valve", and the like, and such terms are to be read expansively zather than restrictively, the description here being made to inform those skilled izt the art of the concept of the invention and some of its embodiments, but not so as to restrict the claims set out herein.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic view of the apparatus and method, illustrating one embodiment of the invention.
Figure IA is a schematic view of the apparatus and xz~ethod, illustrating a second embodiment of the invention.
DETAILED DESCIZIFTION OF THE INVENTION
The following description relates to one embodiment of the invention, and is made with reference to Figure l, which is a stylized schematic drawing of an exemplary gas producing well, including the apparatus of the present invention. A
well bore 5 containing the apparatus extends from surface 10 ax<d passed into or through a gas-producing reservoir 12. Well bore 5 is lined with casing 16. As is knawn, perforations X8 are farmed through ~sir~g x6 adjacez~t reservoir 12 to permit reservoir fluids to enter the bore of the casvzg. 'f'he azunulus about casing 16 is filled with cement or other sealants such that migration of fluids therethrough is avoided and instead fluids pass through perforations into the casing.
zz A check valve 20 is installed in casing 16 above perforations 18. Valve 20 permits passage of fluids upwardly therethrough but seals against passage of fluids downwardly towards reservoir 12. The valve can be a permanent installation or can be more tempos ary in nature. Valve 20 can be any of ~~arious check valves such as, for example, a ball valve or a sprung flapper valve.
A tubing string 26 extends within casing 16 from surface 10 and has a lo~~er, open end 28 positioned above check ~~alve 20. With tubing string 26, two conduits are provided for passage of fluids from reser~~oir to surface. The first conduit is the annulus 30 between casing 16 and tubing 26 and the second conduit it through the inner bore of tubing string 26. Val~~e 20 contr ols the passage of fluids from the reser~~oir to the two conduits.
1 ~ The tubing string can be a string pre~~iously r un into the well for production or production-enhancement purposes or can be run in for the purpose of unloading the ~n~ell bore of water. While tubing string 26 is preferably formed of standard production tubing, other tubing materials can be used.. In any e~~ent, the tubing skiing must be able to withstand pressure differentials across its walls and must be able to support its own weight in the length required to extend from its hanger at or near surface to just abo~~e the check ~~al~~e. It should be of inside diameter sufficient to efficiently move water in the required ~~olumes ~n~ithin reasonable amounts of time ~~ith reasonable energy expenditures. In addition, the tubing string should have an outer diameter selected with consideration as to the casing's inside 2~ diameter to permit efficient mo~~ement of gas past the tubing string over its length.
In conventional production ~~ells, tubing string diameters can be of various sizes and still be used in this invention. Typical diameters are 1/2", 3/4", 1", 1 1/4", 1 1/2", etc. The only requirement to operate this invention is that the tubing string's bore (if it is used as the exhaust conduit) has to be of a size that the liquids being remo~~ed do not flow down past the gas flowing up the conduit (for example, 3 1 /2" outside diameter tubing is too large if installed in a ~" inside diazxtete~r casing, as the compressed gas bubbles through the liquid, the liquid flows down past the gas, and in both instances the liquid is not produced to surface to unload the well).
Lower open end 2$ of the tubing string represents the lowest level to which water can be unloaded from the well. Thus the tubing string must be extended down to a level selected with consideration as to the column of water that will be left in the well and the pressure of the gas in the formation. In particular, the tubing must be low enough such that the reservoir gas pressure exceeds the hydrostatic pressure of a water column extending to lower open end 2$. In one embodiment, end 28 is 0.01 - 3.0 meters above the check valve and the check valve is located just above, for example, 0.5 - 3.0 ~metexs, the highest perforation in the casing.
A casing valve 31 is provided at well head 32 which permits closure of either or both of tubing string 26 or annulus 30. Casing valve 31 permits various of the wellhead rnrnponents 32 above it to be rexmoved, while the well is shut down.
At the well head, a seal 3~ is positioned in annulus 30 to seal against the passage of fluids. 'This may be in the form of a coiled tubing hangez~, for example.
Above seal 34, tubiaxg string 2b opens into a conduit 40 leading to a gas collection system (not shown) including gas/liquid separators, and communication to pipelines, etc. Thus, any fluids, such as gas or produced water, Flowing through tubing string 26, as will be discussed hereinafter, can be passed to the collection system.
Below seal 34, a conduit ~2 opens through casing 16 into annulus 30. Conduit 42 opens into tyro further coxiduits 44 and 46. Conduit ~, which can be closed by a valve ~S, pexznits flow of gas produced tluough the casizig azululus 30 to a gas collection system 55 including gas/liduid separators, storage facilities, compressors, access to pipelines, ete. Conduit 46 is in communication with a source 49 of pressurized gas, controlled by valve 51, and permits floe of pressurized gas therethrough to annulus 30. The sour ce of pressurized gas can be air or produced gas from a compressor or gas from a high-pressure source such as a nearby high pressure well bore. Where a gas produced by a high pressure gas well S is used, no compressor will be needed. However, when using either a hlgh pressure gas well or a compressor, various control systems must be used to ensure that gas is introduced to the well only at selected times and for selected duration's or until desired results are achieved.
Seal 34 provided for separate handling of fluids from annulus 30 and fluids from tubing string 26. As will be appreciated, other means can be used in place of the seal to maintain separate fluids from these two conduits. It will also be appreciated that other conduit arrangements can be used for effectively permitting introduction and removal of gases and liquids from the well bore.
1~
The apparatus as described IllaS' be used in the follo~~ing Illethod to de~n~ater a gas well. When the reservoir 12 produces gas, it passed through perforations and into casing 16. After passing through the check valve 20, the gas passes through annulus 30 and is collected through conduits 42 and 44. Alternatel~~, produced gas can pass up both annulus 30 and tubing string 26 and be collected at surface therefrom. In another embodiment, tubing string can be removed during regular production and only run in for unloading of produced water, when necessary.
2~ In some wells, eater 52 is produced and may collect at the well's bottom.
Eventually the ~n~ater level in the ~n~ell bore ~n~ill attain a height such that its h~~drostatic pressure impairs the production of gas from reservoir 12 using the reservoir's inherent pressure. This causes a decline or even cessation of gas flow from reservoir 12 to surface 10 for collection. In those circumstances, the apparatus described can be actuated to remove that accumulated w=ater and other liquids.
~s When the appaxatus is used to remove water 52, check valve 20 must be dosed. The check valve can be closed by the hydrostatic pressure of water above the check valve exceeding the pressure ~~co~an reservoir 12 below the check valve.
Alternately, check valve 20 is closed by introduction at wellhead 32 of pressurized gas from source 49 (i.e. by c~osuz~e of valve 48 and introduction of gas through rnnduits 46, 42). A combination of those forces can also be used to close the check valve.
ice check valve 20 is closed, pz~essurized gas is introduced into the casing 14 annulus 30 from source 49, as indicated by the azxows G, which causes a pressure increase above accumulated liquid at the well's bottom. Seal 34 prevents any introduced gas from passing to conduit 40, thus all gas passes down through axunulu5 30. Eventually, the pressure of the introduced gas exceeds the hydrostatic pressure of the accumulated liquid 52 and the pressure of the fluid in tubiz~g string 26 above the liquid. This causes the tubing string to behave as a siphon and the accumulated liquid 52 to be thus forced to flow, as indicated by arrows W, to surface 10 and out through conduit 40 to a collection system 65.
It will be appreciated by those skilled in the art that the source of pressurized gas will be required to provide sufficient gas to fill and pressurize the sealed casing. The volume of casing to be filled is easily calculated by reference to the casing's inside diameter and its length. Preferably, sufficient gas should be available to also fill the tubing siring within the casing. The gas must be eventually at a pressure greater than the hydrostatic pressure of the accumulated water, which pressure can be easily calculated by the accumulated water. Thus the pressures and volumes of gas required can be quite easily calculated using known information. For example, in a typical test well, equipped with 4 12/" casing and 1 1 /2" coiled tubing, and with reservoir pressure approximating 130 psi az~d well depth of 530 meters (1740 feet), the hydrostatic pressure of a column of water within the casing of z6 approximately 280 feet overcame the formation production pressures, at which stage the ~n~ell ceased production (280 feet of salt-laden water equates to approximately 130 psi at bottom of the column). Gas was introduced to the ~n~ell into the casing and reached a pressure of up to 750 psi at its maximum (since that is the pressure induced by a 1 1/2" diameter column of salt-laden eater 1740 feet high, being the exhaust tubing during the time when it is filled during the unloading exercise). The above numbers are annr~ximat;r",~ fnr Aaco ~F
description, and ~~ould vary with the salinity of the produced water and the depth of the well and its formation pressure. From this example, ho~n~ever, it is apparent that the pressure ranges for the introduced gas can be readily calculated from known or easily obtained information at the ~n~ell-site.
Gas can continue to be introduced until all of the accumulated liquid do~~n to the level of end 28, as indicated b~~ introduced gas exiting through conduit 40, or 1 ~ for a selected period of time. When a selected amount of accumulated liquid is thus evacuated to surface and out of the well, the flow of pressurized gas is stopped.
The valve 48 is opened, and the pressurized gas ~~ithin tubing string 26 and annulus 30 is aIlo«~ed to dissipate through conduits 40 and 42 to collection systems, ~1'I11CI1 typically include separators, compressors and pipelines, etc. Once the pressure of introduced gas is sufficiently dissipated and provided a sufficient amount of introduced gas is sufficiently dissipated and provided a sufficient amount of water has been removed, the check valve 20 opens and permits passage of produced gas from reservoir 12. Produced gas then continues to flo~n~ up through the casing to surface until produced «~ater accumulates such that the check 2~ valve is again closed for ~n~ater removal.
While the described route of water removal is up through the tubing str ing, it is to be understood that the reverse operation could be used (by altering the valve seal and pipe configuration at surface) ~s~herein compressed gas is introduced through the tubing string to force accumulated water up through the casing annulus.
It will be apparent that the introduction of pressured gas can be initiated automatically or manually, and may be responsive to a timer, a pressure differential sensor system, a drop in production volumes which indicates an increase in accumulated liquids at bottom-hole, or other suitable indications.
A person skilled in the art will understand that when the liquid is exhausted from the casing annulus 30 above lower open end 28 of the tubing string 26, there will then be a large volume of introduced gas passing up through tubing string to the collection system. In addition, there ~~ill be large volumes of introduced gas to be handled when the introduced gas is allo~~ed to depressurize. Thus, flo~.v control means and perhaps chemical injection means would profitably be utilized to 1 ~ r educe such deer essurization and the commensurate temperature drops and consequent hydr ate formation and other mechanical problems associated with such events.
It «~ill be understood that various changes in the details, materials, ar r angements of parts, and operating C011d1t1onS ~-1'111c11 have beeI1 described and illustrated here in or der to explain the nature of the invention may be made b5~ those skilled in the art ~n~ithin the principles and scope of the invention, and will not derogate from or limit the scope of the claims.
~s

Claims (19)

WHAT IS CLAIMED IS:

1. An assembly for production of gas from a down-hole gas-producing formation to surface through a well bore lined with casing having openings through which gas can pass from the formation into the casing, the assembly capable of being periodically cleared of accumulated liquids when the pressure of produced gas is insufficient to overcome hydrostatic pressure of the accumulated liquids, the assembly comprising:
a. a tubing string extending from surface through the casing and having a lower open end positioned below a point at which the hyrdrostatic pressure of the accumulated liquids exceeds the pressure of produced gas, the tubing string having a bare sealed from fluid flow communication with the casing except through the lower open end;
b. a check valve positioned and sealed to the casing above the openings and below the lower open end of the tubing string, the check valve permitting flow of fluids from the openings toward the lower open end of the tubing string, but restricting reverse flow therethrough; and c. a means for introducing pressurized gas from a source at surface to either the casing or the tubing string to create a pressure in excess of the hydrostatic pressure exerted by the column of accumulated liquids above the accumulated liquids to push the accumulated liquids from bottom hole up through the other of the casing or the tubing string to surface and out of said well bore.

2 The assembly of claim 1 with a means of collecting fluids passing from the tubing string to surface.

3 The assembly of claim 1 with a means for collecting fluids passing from the casing at surface.

4 The assembly as in claim 1 wherein said tubing string is an existing tubing string placed within said casing as part of a production program.

The assembly in claim 1 wherein said check valve is a ball-and-seat valve.

6 The assembly in claim 1 wherein said check valve is a sprung flapper valve.

7 The assembly in claim 1 wherein the source of pressurized gas is a compressor.

8 The assembly in claim 1 wherein the pressurized gas is air from atmosphere at surface.

9 The assembly in claim 1 wherein the pressurized gas is gas collected at surface from the formation.

The assembly in claim 1 wherein the pressurized gas is collected gas from another well.

11 The assembly in claim 1 wherein the means for collecting fluids passing from the casing at surface is a conduit including a valve for controlling fluid flow therethrough and connected to a gas collection system.

12 The assembly in claim 1 wherein the means for collecting fluids from the tubing string at surface is a conduit leading to a gas collection system.

13 A method of unloading accumulated liquids from a well bore to a level sufficient to permit gas to be produced from the well bore, the well bore being lined with casing and having openings in the casing to permit produced gas to pass from a formation into the casing, the method comprising:
a. providing an assembly including a tubing string extending from surface through the casing and having a lower open end positioned below a point at which the hydrostatic pressure of the accumulated liquids exceeds the pressure of produced gas and above a check valve, the tubing string having a bore sealed from fluid flow communication with the casing except through the lower open end; a check valve sealed to the casing above the openings and below the lower open end of the tubing string, the check valve permitting upward flow of fluids from the openings to the lower open end of the tubing string, but restricting reverse flow therethrough; and a means for introducing gas from a source of pressurized gas at surface to either the casing or the tubing string;
b. closing the check valve;
c. introducing gas from surface to either the casing or the tubing string to create a pressure in excess of the hydrostatic pressure exerted by the column of accumulated liquids above the accumulated liquids to push the accumulated liquids from bottom-hole up through the other of the casing or the tubing string to surface and out of said well bore; and d. stopping introduction of gas from surface to permit the well bore to return to production of gas from the formation.

14. The method in claim 13, further comprising the step of collecting fluids passing from the casing at surface.

15. The method in claim 13, further comprising the step of collecting fluids passing from the tubing string at surface.

16. The method in claim 13 wherein the step of closing the check valve is accomplished when the pressure of the accumulated liquids above the check valve is greater than the pressure exerted below the check valve by the formation.

17. The method in claim 13 wherein the step of closing the check valve is accomplished by introducing gas from surface such that the pressure above the check valve is greater than the pressure exerted below the check valve by the formation.

18. The method in claim 13 further comprising determining when the check valve is closed by observing when the flow of produced gas has ceased.

19. The method in claim 13 wherein said accumulated liquids are forced to surface through the tubing string and out through the means for collecting fluids passing from the tubing string at surface, the means including an apparatus providing for separation of liquids from gases.