RU2529197C1 - Drilling wastes underground burial - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention can be used in permafrost regions with hydraulically isolated lenses of underground smelt water bearing sand collectors, cryopag (CP), for burial of drilling wastes (DW). Proposed method comprises drilling of one injection well in CP and at least one CP relieving well. Besides, it includes pressure pre-decrease in CP by forcing water-sand pulp via said CP relieving well. Decreased pressure stabilised in injection well, uniform mix of drilling wastes and at least 10 wt. % of crushed ice made from sea water or water pumped from CP with additional of the mix of fluid hydro geological indicator (HGI). Note here that drill wastes are continuously subjected to audio frequency vibrator effects nearby suspended tubing shoe. Injection is continued unless HGI traces appear in pulp forced from relieving well. Then, drilling waste injection into CP, their vibration and pumping of pulp from CP are terminated to eliminate RW. For burial of extra volume of drilling wastes, another RW is constructure to go on injecting of drilling wastes via the same IW with their vibration and application of another RW.

EFFECT: ecologically safe and efficient process.

2 cl, 1 dwg

Description

The invention relates mainly to the oil and gas industry and can be used for drilling exploration, production, injection, observation, absorbing, flooding and other boreholes in regions adjacent to the shores of the seas of the Arctic Ocean and covered with a thickness of permafrost rocks of high power.

When drilling any exploratory or producing well, a large amount of drilling waste (BW) is generated: drill cuttings in the form of sand-gravel neo-rolled particles of drilled rocks; spent drilling fluids (OBR) in the form of water-clay suspensions containing many different usually harmful additives and additives that regulate the properties of the drilling fluid; drilling wastewater - contaminated with clay particles and the aforementioned additives from water obtained from flushing of drilling tools and equipment and usually comprising about 70% of the volume of drilling waste. The total volume of BO from one well is usually not less than 300 m ³ , and the total volume from drilling 20 wells of one cluster site can be from 6000 m ³ to 8000 m ³ .

The annual volume of BO during the development of one of the major oil and gas condensate fields on the Yamal Peninsula is approximately 25 thousand m ³ . The average specific gravity of BO is 1250 kg / m ³ , the freezing temperature is -2 ° C.

There is a method of burial of BW in underground caverns developed by thawing permafrost sand deposits or ice in the depth interval from 15 to 100 m from the surface of the earth in accordance with patent RU No. 2438953. The disadvantages of this method are the time, labor and material resources for the preliminary construction of underground reservoirs, the lack of geocryological conditions necessary for the construction of underground reservoirs in the right places, the risk of squeezing buried BO to the surface due to subsidence and dips of the overburden thawed during construction of rocks, as well as Significant areas of land surface contamination with alluvial maps (hydraulic dumps) extracted to the surface of water-soil pulps s (AHP).

Closest to the proposed invention is the injection of liquid industrial waste into deep porous rock reservoirs through absorbing wells (see Mining. Development and conservation of the bowels of the earth. Edited by Academician KN Trubetskoy. M.: Publishing House of the Academy of Mining Sciences , 1997, 478 p .; p.25). The disadvantages of this method are the high cost of drilling and operating absorbing wells (usually with a depth of at least 700-1000 m), a serious environmental risk of groundwater pollution, including of aquifers of drinking water due to the uncontrolled distribution of waste pumped into underground reservoirs, as well as the need for periodic recovery of declining injectivity of absorbing wells or even the construction of additional wells to replace failed ones.

The aim of the invention is to overcome these shortcomings in the oil and gas fields of the Far North, for example on the Yamal Peninsula, based on the use of the specific geocryological structure of the permafrost rock mass (IMF) of Yamal, as well as regions adjacent to the shores of the Arctic Ocean with similar geocryological conditions, including on a shallow shelf.

The aforementioned specificity is that the thickness of the permafrost with a total thickness of usually at least 300 m, is two- or even three-layer, and comprises almost everywhere local hydraulically isolated lenses of thawed underground aquiferous porous sand collectors - cryopegs, the pores of which are filled with saline water under a pressure of 30 to 130 m water column (i.e., a pressure of 3 to 13 kg / cm ² ). The salt composition of cryopegs is similar to the salt composition of sea water, and the salt content is the same or higher than the salinity of the sea water from which they were formed, as a result of which this saline water does not freeze at temperatures from -1 ° C to -4 ° C. When pumping water from the cryopag through the well, flow rates of up to 20 m ³ / day were obtained with a permeability coefficient of K = 2.5 m / day with a pressure drop of 1 kg / cm ² . Moreover, such brine lenses are located at different depths from the first meters to 200 m from the surface, and the static groundwater levels in the lenses are different, usually they are 5-10 m below the ground surface and well above sea level in the wells, which convincingly indicates the absence the hydraulic connection of such lenses both with the sea and with each other, that is, about their isolation in natural conditions for long periods of time (hundreds and thousands of years).

Saline waters of cryopegs are not valuable for technical or drinking water supply and can be used only for the preparation of fresh drilling fluids, in which, when mixed with fresh water, chloride salts, similar in composition to the salts of sea water, are usually added.

This goal is achieved by the fact that at least one injection (absorbing) and at least one unloading (water) well located within the radius of mutual hydraulic influence in the porous collector of the cryopag, for example, at a distance of 50 to 100 m, is drilled to the bottom of the cryopeg lens from friend. The boreholes are fastened to the roof of the cryopag with cemented casing strings, equip the absorbing well with a discharge suspension string with an open lower end above the bottom of the cryopag, and the discharge well with a hydrogeological filter in the cryopag interval and, if necessary, a suspension string with an open bottom end and a pipe (air duct) inside for pumping water through it from the surface of compressed air and airlift lifting along a suspended column (annular space between it and the air duct) or sand the pulp to the surface.

A concrete pump and a receiving hopper are installed near the mouth of the injection well for unloading into it transported from boreholes in concrete mixer trucks intended for burial of BW, an ice maker, as well as a dosing pump for pumping a liquid hydrogeological indicator and a control borehole vibrator into the BW stream, such as those used in construction for compaction of concrete, which is lowered from the surface to a mark below the end of the discharge suspension column.

Saline water or water-sand slurry is pumped to the surface in advance from the discharge well with a flow rate, for example, 10 m ³ / h, exceeding the design average averaged flow rate of injection into the absorbing well BO, for example 3 m ³ / h, until a decrease is established as a result of such pumping, the level of saline water in the annulus of the casing and suspension strings of the injection well, which indicates the establishment of an almost stationary hydraulic regime for pumping pulp from the cryopag.

The pumped-out saline water after its sedimentation is partially used to prepare granulated ice from it in an ice generator to mix it with the mass of stored BO, and the rest of the water is transported to drilling sites for the preparation of fresh drilling fluids.

After that, the concrete pump is pumped through the suspension string of the injection well, a complex mixture of all types of BOs substantially uniformly mixed in the mixer, including drill cuttings and liquid BOs with finely crushed, preferably saline ice above the cryopag sole with continuous low-amplitude vibration of the injected mass by a vibrating sound frequency vibrator, for example, 50 Hz, moreover, a liquid hydrogeological indicator, recognized after repeated breakdown, is injected into the flow of injected waste with a metering pump Lenia. In the process of pumping waste, the level of saline water in the annular annulus of the injection well is constantly monitored. If the static initial pressure is exceeded, the injection of BO is temporarily stopped or the injection rate is reduced until the water level in the well drops to the level at which BO injection was started.

The BO injection into the cryopag is continued (periodically or continuously) until persistent signs of indicator fluid are detected in the water pumped from the discharge well to the surface, indicating that the most mobile part of the buried BO has overcome the distance between the wells and began to flow through the unloading well to the surface of the earth. After that, the injection of BW into the injection well and the pumping of water from the discharge well is stopped, the burial of BW in the area between these wells is considered completed, the discharge well is liquidated, if necessary, the burial of new BW will be replaced by the replacement of a new discharge well located, for example, symmetrically relative to the injection, and carry out further burial of BO between the injection and the new discharge well, continuing this process, if necessary, several more times (for example, up to 8).

Let us explain the need for the proposed sequence of operations of the method. The most important condition for the environmentally safe implementation of the proposed method is the guaranteed prevention of hydraulic fracturing of the permafrost layer covering the cryopeg. In the case of the usual injection of liquid BOs into a cryopag through a sealed well without preliminary hydraulic unloading of the cryopag, the liquid pressure in it, as in a hydraulically closed system, will inevitably increase even after a certain excess of the natural pressure (for example, by the order of 3 kg / cm ² , exceeding the usual long-term tensile strength of frozen rocks) hydraulic fracturing of the overburden in the form of an approximately vertical crack or a system of such cracks will inevitably occur with all negative consequences for the environment.

Anticipatory areal hydraulic unloading of the cryopeg from natural (and even more than exceeding it) pressure, achieved by continuous pumping of water or water-sand pulp from unloading wells, allows reliable and continuous monitoring of the actual pressure during the entire burial of BO and prevents a steady excess of natural pressure in the cryopeg within the radius of the effect of pumping from the unloading well and to maintain depression in the direction from the injection to the unloading well, providing an advantage substantial distribution of buried BW in the cryopeg in the direction from the injection to the unloading well. Continuous monitoring of the water level in the annulus of the casing and suspension strings of the injection well allows you to constantly monitor the actual pressure in the cryopeg and, if necessary, prevent its increase, for example, by temporarily stopping or reducing the injection rate of BO.

Fluid BO injected under excess pressure above the cryopag sole usually has a positive temperature before injection, which can cause thawing of the IMF behind the casing string. The addition of at least 10% by weight of crushed slightly saline ice thawing at a temperature of about -1 ° C allows you to quickly cool the injected flowing BO to a temperature below 0 ° C and prevent such thawing and depressurization of the annulus of the injection well. At the same time, melt water formed approximately uniformly in volume of waste further dilutes the volume of BO pumped into the cryopeg, reduces the viscosity of the stream when the BO moves down the suspension column and hydraulic friction losses, and contributes to their better spreading in the cryopeg collector in all directions from the shoe of the suspension discharge column. In this case, the angle of friction and the angle of repose of the waste mass at the boundary with the rocks of the reservoir are reduced, which contributes to better replacement and displacement of the rocks of the reservoir under the influence of the pressure difference between the injection site and the unloading well. This process stimulates continuous vibration of the mass of injected waste, which also reduces their effective viscosity and facilitates the spread of waste throughout the cryopag, including due to the partial replacement of saline water in the pores with a clay slurry OBR.

The technological scheme explaining the proposed method is shown in figure 1, in which:

1. Permafrost sedimentary rocks (IMF).

2. The sole of the thickness of the permafrost.

3. The characteristic natural temperature of the permafrost.

4. Isolated MMP pressure-bearing aquifer (“cryopeg”).

5. Injection well for injection of drilling waste.

6. Suspended discharge column for injection of drilling waste (BO).

7. Unloading well for pumping water-pulp from the cryopag 4.

8. Casing strings of wells.

9. Cement shell casing 8.

10. Pulp lifting suspension column.

11. Air supply suspension column.

12. Anti-sand hydrogeological filter in the depth interval of the cryopeg 4 in the discharge well 7.

13. The reservoir with indicator fluid.

14. Dosing pump for supplying indicator fluid to the BO stream.

15. The control point of the vibrator 24.

16. The pump for the injection of BO on the column 6.

17. The mixer for mixing BO with ice granules.

18. Ice maker.

19. The receiving bunker BO.

20. Concrete truck with BO.

21. Compressor for supplying compressed air to the column 11.

22. A hopper for receiving and settling pulp.

23. Sandy dump of sludge sludge.

24. Vibrator.

25. Clay paste over a layer of sludge.

26. Drill cuttings above the bottom of the cryopag 4.

27. Directions for filtering buried drilling waste.

28. The initial static pressure level of groundwater cryopag 4.

29. Quasi-stationary groundwater level of a cryopeg as a result of pumping water-sand pulp from an unloading well 7.

The proposed method is as follows.

In cryopag 4 isolated by permafrost rocks 4, an injection well 5 is drilled for injection of BO and an unloading well 7 for pumping out water-ground pulp. Cryopag 4 is characterized by an initial static groundwater pressure level of 28. Wells 5 and 7 are cased with columns 8 and fixed with cement sheaths 9.

In the casing of the well 7, a pulp-lifting suspension string 10, an air-supplying suspension string 11 are lowered to create airlift mode in the annular annulus of the suspension pipes 10 and 11. The head of the well 7 is sealed, the column 11 is connected by a pipe to a compressor 21 for supplying compressed air, and the column 10 with a hopper 22 for receiving and settling sandy water pulp. The unloading well 7 in the interval of the cryopeg is equipped with a hydrogeological anti-sand filter 12.

Prior to the arrival of the buried BO from the cryopag 4, the leading hydraulic discharge is effected through the column 10 by pumping salted water or water-sand pulp from the cryopeg to the surface, while the water level in the annulus of the casing and suspension columns of the injection well is continuously monitored (actual water pressure in the cryopeg) and when the quasi-stationary pressure in the cryopeg 29 is reached, which is lower than the stationary level 28, they start supplying the BO to the cryopeg 4 through the injection well 5. During the BO injection, the quasis control stationary pressure in cryopeg 29 allows you to quickly adjust the flow rate of injected BOs and prevent its increase by reducing the flow rate of injected BOs or temporarily stop the injection.

The water-sand pulp pumped to the surface enters the hopper 22, from where solid sediment enters the dump 23 for disposal or further use for filling the drilling sites, and the saline water partially enters the ice maker 18 for preparing granulated ice and mixing it with the mass of buried BO, and the rest water is transported to drilling sites for the preparation of fresh drilling fluids

A suspended working column 6 is lowered into the borehole 5 for injection of BO, the open lower end of which is located above the sole of the cryopag, and the vibrator 24, controlled from the control point 15 and lowered approximately a mark below the open lower end of the injection suspension column 6. The head of the well 5 is sealed, the column 6 are connected by a pipeline to a pump 16, which from the mixer 17 delivers a mixture of BO coming from the receiving hopper 19 and transported to it from the drilling rigs by concrete trucks 20 from the mixer 17, and ice granules from the ice maker 18, designed to quickly cool injected BO to a temperature below 0 ° C and to prevent thawing and depressurization of the annulus of the injection well 5. In this case, the melt water generated in the waste volume further dilutes the BO cryopaged in the cryopag and reduces the viscosity of the stream when the BO moves down the suspension column 6 and hydraulic friction losses, contributes to better spreading of BO in the cryopag collector in all directions from the shoe of the suspension discharge column 6. This process also stimulates continuous vnaya mass vibration injected waste audio frequency vibrator 24 also reduces their effective viscosity and facilitates the spreading of waste on cryopeg volume, including by partial substitution of saline water in the pores of the clay slurry ON and to prevent freezing of ice crystals in the monolith. In a separate implementation of the method, a concrete truck 20 can be used as a mixer 17, into which ice granules can be fed from an ice generator 18, after which the resulting mixture is unloaded into a receiving hopper 19 and, using a pump 16, feed the resulting mixture of BO with ice granules to a cryopag for burial 4 directly. Column 6 is also connected by a pipeline to the metering pump 14 for supplying indicator fluid from the reservoir 13 to the BO stream.

The BO injection into the cryopag 4 is continued (periodically or continuously) until persistent signs of indicator fluid are detected in the water pumped from the unloading well 7 to the surface, indicating that the most mobile part of the buried BO overcame the distance between the wells and began to flow to surface. After that, the injection of BO into the injection well 5 and the pumping of water from the unloading well 7 is stopped, and the burial of BO in the area between these wells is considered completed.

An example implementation of the method.

At one of the Yamal gas fields, a cryopeg was discovered in the thickness of the permafrost in the depth range from 62.5 to 66.5 m, which is under the natural pressure of groundwater 54 m (5.5 kg / cm ² ).

For burial of 3000 m ^{3 of} drilling waste, injection and unloading wells were drilled at a distance of 75 m from each other, with a depth of 70 m each. Both wells were secured with cemented casing with a diameter of 245 mm to a depth of 60 m, a suspension working string with a diameter of 127 mm was lowered to a depth of 66 m, and a suspension string with a diameter of 168 mm was lowered into a discharge well with a depth of 66 m, equipped with a depth range of 60- 66 m hydrogeological mesh sand filter. A pipe with a diameter of 60 mm was lowered inside a discharge well to a depth of 59 m to supply compressed air.

Compressed air began to be pumped into the unloading well with an NV-10 compressor with a capacity of 10 m ³ / min, as a result of which the airlift pumping of water from the cryopag began with a flow rate (flow rate) of 12 m ³ / h. The salt water pressure in the injection well began to decrease after one day and after 7 days dropped to 52 m (the water level in the well from 7.5 m from the surface dropped to 9.5 m).

About 12 m of ice in the form of granules from 5 to 15 mm in size were made from a part of the salted water pumped out of the cryopag in the ice maker, the rest of the water was taken out in car tanks as process water for the preparation of drilling fluids.

After that, the concrete pump began to pump drilling waste evenly mixed in a concrete mixer truck with 20% by volume of granulated ice with an hourly average flow rate of 3.5 m ³ / h at an injection pressure of up to 12 kg / cm ² . Liquid fluorescein in the amount of 10 ml per 1 m ^{3 of} drilling waste was pumped into the waste stream, and the bottomhole space of the well was continuously vibrated with a 0.8 kW vibrator.

After 28 days of injection with an average daily flow rate of 56 m ³ / day of drilling waste proper (1570 m ³ total), signs of fluorescein were detected in the water of the discharge well. The pumping of water from this unloading well was stopped, instead of this, from the previously prepared symmetrically located other unloading well, a similar pumping of salted water from the cryopag began, and another 1730 m ^{3 of} drilling waste was pumped into the absorbing well for the next 31 days.

After that, the project volume of drilling waste was buried, absorbing and both unloading wells after dismantling suspension columns and equipment from them were eliminated by installing cement plugs, the ends of the wells were cut off, and the earth's surface (tundra cover) was restored over the well sites, leaving warning frames above the wells with the necessary information about the wells.

Claims (2)

1. A method of underground burial of drilling waste in the thickness of permafrost rocks into hydraulically isolated lenses of thawed underground aquiferous porous sand collectors - cryopegs, including transporting spent drilling waste from the drilling rig and pumping it through an injection well into a cryopeg, characterized in that it first reduces the natural static pressure in the injection well and its surroundings by pumping saline water or water-sand pulp from the cryopag through at least one adjacent hydraulically unloading cryopeg well to the surface, after stabilization of the reduced pressure in the injection well as a result of pumping water from the unloading well, a substantially uniform mixture of all types of drilling waste and not less than ten weight percent crushed or granulated ice is prepared preferably from saline seawater or water pumped through a cryopeg discharge well with the addition of If there is a continuous hydrogeological indicator, with continuous low-amplitude vibration of the injected drilling waste using an audio frequency vibrator located under the shoe of the above-mentioned suspension column, the injection is continued until signs of a hydrogeological indicator are detected in the water pumped out of the unloading well, after which the drilling waste is pumped into the absorbing well, its vibration and pumping of water or water-sand pulp from the unloading well is stopped, the unloading well is liquidated, and if necessary, additional An additional volume of drilling waste is equipped with another unloading well and the injection of drilling waste through the same absorbing well with their vibration and with the same use of another unloading well is continued. 2. The method according to claim 1, characterized in that fluorescein is used as a liquid hydrogeological indicator.

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