CA2392831A1 - Vertical flood for improved crude oil recovery from oil pools - Google Patents

Abstract

The above titled invention purports to use of vertical flooding technique instead of horizontal flooding technique along with some improvisations not earlier recognized in oil industry as mentioned above in the background. Only a few operations worldwide are/have been in vogue that used the concepts of vertical flood or gravity stable or toe-to-heal displacement operation. Some earlier works are cited in following US
patents granted already as shown in Table 1. However, all of these as well as all previous oil recovery methods were devoid of following main features that are highlights of current "believed-to-be-future-panacea-technology" in oil industry:

(a) water flood devoid from primary recovery to end (for new field or pools) (b) simple draining concept from primary recovery stage to make viscous fingering or cross flow minimum (c) a much new improved heating concept with some new Physics of thermal /electrical/
electromagnetic heating with a potential gradient or spatially distributed thermal/electrical /electromagnetic potential gradient along the spans of multilaterals that is believed to be capable of generating a much more intense heating due to additional heat flow or current flow paths than normally possible by current technique.
(d) A miscibility generation method with only nitrogen (or carbon dioxide, if nitrogen is not economic) as this is only non-reactive miscibility generating fluid among others and freely available and allows complete sweep to final high pressure nitrogen gas left as stored subsidence preventing reservoir pore space fluid than water with a lot of residual oil in current operations worldwide. An additive to lower minimum miscibility pressure of nitrogen will also be required that will call for search of such chemical in laboratory. One such chemical (as in recycle operation available) is methane gas, as a boon in disguise, in the process methodology suggested (feature 'e' below).
(e) A gas recycling from beginning right from primary recovery stage with methane separated from production stream and recycled as injection stream in gradually decreasing percentage of methane and increasing percentage of mixed nitrogen (or carbon dioxide) gas as the case may be.

Table 1: US Patents granted already on vertical flooding subject US Patent Number(s) Grant Date Patentee(s) US class number 4088190 May, 1978 Fisher et al 166/403 4344485 Aug.,1982 Butler 166/271 4501326 Feb.,1985 Edmunds 166/272 4598770 Jul.,1986 Shu et al 166/245 4682652 Jul.,1987 Huang et al 166/263 4696345 Sep.,1987 Hsueh 166/245 4889186 Dec.,1989 Hanson et al 166/252 5016710 May, 1991 Renard et al 166/245 5054551 Oct.,1991 Duersken 166/272 5065821 Nov.,1991 Huang et al 166/245 5520247 May.,1966 Gmelig et al 166/245 5607016 Mar.,1997 Butler 166/263 5626191 May, 1997 Greaves et al 166/245 6167966 Jan.,2001 Ayasse et al 166/268 It is believed that the total process that requires some affirmative calculations of heating rate improvement and miscibility efficiency as well as productivity index of multilateral drilling design (with minimized cross flow effects of particle flow due to heat and fluid gradients) and overall case study economics of displacement improvement and drilling savings with break even time and project or field life improvement, will be presented in the examination stage of the patent granting as time available for doing it at this application filing stage to avail the priority is necessary immediately. Also the new Physics of heat rate improvement calculation is likely to take some time as such calculations have not been performed before in Physics of electrical or heat or electromagnetic heat engineering. An additional microwave application, devoid of usual steal pipe's low microwave absorption problems upgradable by any new material synthesis in the pipe design is also something that will take time to find. These will constitute the final total method description or specification.

In the basic application filed in India I proposed vertical flooding mainly because an earlier missing point that viscous fingering is minimum, and ratio of vertical to horizontal rate under similar pressure gradient magnitude is high despite adverse vertical to horizontal permeability ratio, as proved in an earlier published paper of mine (JCPT, January, 1999) that area of flow cross section can be used advantageously to achieve this fact. This and other features claimed in this patent application are all annexed in the appendix of this application to show prior segmented arts (not enabling the disclosure of the overall synthesized total process) in my past works. It is indicated which one of these is published and which one unpublished, among these.

Description

Confidential D Ashis Kumar Das, 2001-2002 Vertical Flood for Improved Crude Oil Recovery from Oil Pools Nature of Application Matter: CompYete Specification (NOT FOR SALE) Inventor: Dr. Ashis Kumar Das, Independent Petroleum Engineer (self employed) Priority Patent Application No. 409/CaU01 (Calcutta, India) (provisional specification filed on 26.7.2001) Nationality : Canadian Resident; Eligible US Resident/Citizen; Indian Citizen/Resident;
Address: 28 Doverdale Mews SE Calgary, AB-T2B 1V9, CANADA
Telephone: 1-403-387-0533 Note: Patent Offices) Worldwide and WIPO, Geneva I do not have or never had any legat/medical representatives in courts) of law (if there is court notice(s), send- it to me and me only at my above address) Signature of Ashis Kumar Das (Indian PP No. B 0966003, Can LP No. W922668174) I. Background of the Invention The present invention relates to an unparalleled method of recovery of underground crude oil, from very light to very heavy as well as tar sands, in a novel method yet unaccomplished in oil industry by introduction of a combination of some brand new features in the recovery technology. The brand new features are a simple draining concept right from primary recovery stage that wilt minimize viscous fingering and minimize cross flow effects; a significantly improved heating method that will be applicable to recovery of heavy, very heavy and tar sand oil so far not possible in commonly known thermal recovery techniques; a miscibility enhancing technique with much improved feature by incorporating only nitrogen as miscibility fluid with added chemical for miscibility enhancement i.e.for lowering minimum miscibility pressure ; a gas recycling operation right from primary recovery stage with methane recycled with increasing percentage of added nitrogen gas till end of recovery; and a primarily mainly multilateral drilling concept from as few vertical wells as possible covering the length and depth of the oil pools over all levels or horizons, thus using mainly the vertical flooding direction than the horizontal flooding direction commonly used in oil recovery operations so far which has been rarely used till date. Also some/all segments of the method wilt be applicable to both water flooded oil field (pools} which are in operation already> and for new oil field (pools) especially where the method will best apply as the drilling design with mostly mufti-laterals and a few verticals only will best apply. All my prior publicationslunpublished papers describing many of these basic features in separate presentations, yet not enabling complete disclosure of this total very productive / economic concept, are attached with this application for proving all prior arts from my conceivings till date.
As described in my basic application in India (Calcutta Patent Office of Government of India) with priority for international filing and using the supported copyrighted (with CIPO, Canada) unpublished volume (with original handwritten versions of manuscripts available with me for priority determination) this invention must be patentable in all oil producing nations under my inventorship name.

III. Details of Difference from Prior Art The major difference of this invention which is believed likely to be a panacea technology of future of oillgas recovery for all types of oil viscosities (low to million centipoises) are as described in details one by one below:
(a) Simple Draining Concept: All or most earlier recovery operations of crude mineral nil involved horizontal flooding between vertical wells which had a serious problem in raising a haphazard pressure isobars after some extent of flooding which is half the reason for low recovery in overall oil draining mechanism's efficiency tilt date in my opinion. In the recent unpublished paper of mine ( tilted "A Proposed Paradigm Shift Approach to Oil Field Drilling/Production Strategy for improved Economics" and composing as one paper in the unpublished copyrighted by CIPO, Canada volume tilted Some Advanced Concepts ire Petroleurn Engineeri>tg and Related Applications, which was submitted for publication in JCPT, Canada and for presentation in CIPC
2002 organized by Petroleum Society of CIM, Canada but refused on both occasions by them2 I
proposed for the first time in the history_of oil and gas industry world wide that vertical flooding will eliminate it totally or to a large extent (may be improved by analytical / numerical optimization under constraints for flood front profile evening technique in future as part of usual numerical modelling associated with planning oil recovery strategies) and will be beneficial to greater recovery by reduced viscous fingering in alt subsequent recovery stages such as secondary, tertiary , especially in operations involving liquid liquid interfaces, such as in aqueous operations.
Figures 1 and 2 show the concept elaborately (annexed in the Figure section below). Basically, the isobars are parallel and less curvaceous and gradually decreasing from bottom to top in a manner yielding very high pressure gradient (because of choice of production well pressure held) and very low viscous fingering.
(b) Water Flood Devoid Operation: This has been proposed by me since quite some time in the past in some of my publications as welt and in some lectures and proposed undergraduate theses at Indian School of Mines, India. This presented method clearly shows that completely water flood devoid operation is possible and should be adopted for all oil fields (except may be aquifer supported ones where some aquifer intrusion into vacated oil pores will cause preferential fingers of water). The relevant publicationslunpublished manuscripts are attached in the annexure.
However, the method's some features will apply to the water flooded fields as well. Ideally, I will propose absolutely no water flood in all new discovered oil fields in the world to si;nificantly improve oil recovery displacement efficiency. In addition the simple draining induced favourable pressure isobar will add to recovery efficiency very much.
(c) The New Improved Heating Based on Generalizing Uld Concept: In an earlier JCPT
publication (Petroleum Society, CIM; Canada) I showed how rate of particle or radiation transport depends on ~ (potential strength x area of cross section of flow x conductance magnitude).
This concept has been more or less added-upgraded by conceiving a spatial potential gradient distribution such as T(s), E(s,t) or H(s,t) in thermal or electrical and electromagnetic mode applications which were missing so far. This is illustrated in Figure 3. This will enable heating or electric current. paths that are not one dimensional as commonly seen in electrical engineering applications' but 2 and 3 dimensional. This means that more intimate heating and heating rate, upgraded by the arealvolume of cross section increasing as the recovery continues (increasing area or volume occupied by conductive path) will result (in water flood cases due to increasing saline region occupying the pore volumes, or in non-aqueous cases due to swelling immobile water with release of pressure although not as much as in aqueous cases) . Note as shown in Figure 4 that instead of one dimensional flow of electron current, especially in the case of electrical or electromagnetic heating , volumetric flow will result due to spatial difference of potential Confidential . ~ Ashis Kumar Das, 2001-2002 gradients (E (s,t) or H(s,t) ) . The details of calculation will take some time and will be taken up in post - examination stage recommendation for amendments. This is currently part of my ongoing Petroleum Engineering doctoral dissertation (self guided/supervised) at University of California, Berkeley and is so protected from infringement. Possible use of microwave heating with such gradient potential arrangement is also being explored to improve heating time in very viscous tar sands cases.
(d) Gas Recycling Concept Right from Start of Primary Recovery Stage: This has been proposed by me in some past publications and is a part of the currently proposed method in making up the total concept especially for new fields. Ideally, in any pool of a tiered oil field (multi level) the produced stream will be subjected to separation of oil from gas (methane mainly) and the gas will be reinjected right from start of primary recovery (unlike now) with increasingly mixed amount of nitrogen gas (or carbon dioxide if nitrogen is not economic for pumping) and an added chemicallgas (in later stages of pumping when methane percentage in recycle stream will be less) to improve minimum miscibility pressure (MMP) of nitrogen (or carbon dioxide).
If X/m scf/bbl is soluble at a given reservoir pressure and temperature than an added chemicallgas will take it to [(X
+ Y) scf of nitrogen + Z scf chemical/gas ] / [ m+n ] bbl oil whose overall value as compared to non-additive case will depend upon tested search taking note of Hildebrandt's solubility parameter and its effect on such studies as stated by me in my earlier papers. In this connection a reference is drawn to a new concept raised by me , one that was earlier missed in injection operations in oil recovery, that of availability of net reservoir pressure boosting by raising the injection temperature from surface (room or ambient) to reservoir temperature and net temperature beyond (due to density and pressure increase at higher rate in confined space than in open space). This means that MMP lowering may not be required to that extent as commonly understood, as some pressure boosting will be available from this surface to reservoir and final net temperature raising causing additional (over the reservoir pressure) final net reservoir pressure. The annexure attached show a list of several concepts in brief description (ongoing detailed studies of these never- "profusely" -before- in -petroleum- engineering- literature materials) which elucidate this concept in great details (from unpublished CIPO, Canada copyrighted by me alone volume titled Some Advanced Concepts in Petroleum EnQiueering and Related Ap~ications, last section with list of 25 itemized research briefs from which item numbers 17, 18, 20 and 22 are to be considered especially).
(e) A Multilateral Drilling Concept to Reduce Number of Vertical Wells:
Profuse use of multilaterals drawn from a few starting vertical wells, than mostly/only verticals (or close spaced spot pattern vertical wells as in many past or ongoing especially secondary/tertiary recovery operations which is very costly) as shown in Figure 5 is definitely going to improve the overall drilling cost and will systematize the updating of economics of drilling deeper horizons. In each pool, the pool reserve will be calculated based on a early time well test or equivalent reserve determination technique as deeper and deeper horizons are drilled. The resulting productivity index for the multilaterals placement requires detailed calculation which will be given in final form of the patent application when examined for patentability and upgrading/amendment. Some cross flow resulting from upward vertical flow between adjacent laterals is expected but still the simple draining derived advantage will be generally mostly available. Some design can be done to assure this convincingly, it is imperative indeed.
(f) Special Feature in Case of Water Flooded Pools/Field: As discussed in my basic application in India, in the cases of prior water flooded pools (already producing ones with mostly vertical wells), the vertical flood can still be applied with confining of introduction of water/aqueous chemicals) from bottom few feet of well adjacent to bottom bed boundary and producing the oil from top few feet of wells) , as shown in Figure G (a and b) which will be assisted better if simple drain as above in (a) is available for application from primary recovery stage. However, in case of prior vertical wells based primary recovery, the pressure isobars will be haphazard, yet depending on injection pressure magnitude; the generally vertical rise of secondary flood front will be achievable, however, with reduced evenness of flood front or water-oil interface in vertical propagation direction. The detail calculation will be shown in later recommendation stage of this patent application examining.
(g) A Separate for-Future Aspect of Assessment for Exploiting Hydrocarbon Pools a Hydrogen and COZ or Other Gaseous Products Only: Reaction analysis urging for FOR
(enhanced oil recovery) injections was first given my me in my MS and ME degree research on surfactant Confidential ~ Ashis Kumar Das, 2001-2002 polymer flooding at University of California, Berkeley in 1983. In that line it revealed (surprisingly not by anybody earlier as they did not focus on reaction analysis urging) that common water (immobile or mobile in gaseous stage especially, i.e. in steam mode) and methane should react under high pressure, temperature, surface area, catalysts (or foulers may reduce reaction rate) and long time conditions to generate hydrogen gas whereas CZ+
can be made to react in partial oxygenation way to also reduce heavier hydrocarbons to hydrogen. In both cases the other product will be carbon dioxide gas. Thus chances of all carbon recovery useful for petrochemical industry will also be available. However the "overall utility and conversion assessment" for total fuel recovery efficiency and petrochemicals exploitation economics is on card during post-examination amendment of this patent application that is being filed quickly to avail international filing coverage.
IV. Detailed Steu By Step Methodology (a) for non-aqueous or aqueous methods:
( 1) Strike oil in the first discovery vertical well:

(2) Obtain upper and lower pool boundaries from logs already obtained.

(3) Carry out short time well tests (without much disturbing the initial pressure over most of the pool volume) to get the shape and the size of the pool (for which new well test interpretation method may have to be developed or other information source may have to be utilised), and initial reservoir or pool pressure (may also be from DST with bottom hole sample collection).

(4) Get dip of the pool from dipmeter log. Also get pool reserve from use of sonic and resistivity logs.

(5) (a) Drill into deeper horizons in the discovery well until newer pools are found and with accompanying stepwise procedures 2 through 4.
(5) (b) Drill a few more wells updip and/or downdip to cover the lateral extent of the pools) evenly covering the 2D areal extent of the pools) (Figure 5). Update reserve calculation with more log informations from these wells.

(6) Depending on the thickness of pools) encountered upto the target depth, drill multilaterals/drainholes (may not be possible in thin pools) for primary recovery from each pool. Each pool multilateral should be extended through out the lateral extent of the pool limit on the concerned end (as shown in Figures 5 and 6) and should be placed as close as possible to the respective upper pool boundary. However, technical feasibility of drilling such multilaterals/drainholes, especially the placement accuracy, is currently being studied. It appears that to reduce the number of mutilaterals/drainholes one can have the option of exploring long radius drainholes with larger turning radii, which has not been shown in Figures 5 and 6 explicitly.

(7) Carry out primary production through these multilaterals at preferably constant pressure held in the multilaterals to design "bottom-to-top"uniformly decreasing level post-primary-3D-isobar scenario in each pool covering the 2D areal extent of the pools) as seen in Figure 5.

(8)(a) In thin pools exploit secondary vertical flood with vertical wells as in primary phase.
(8)(b) In thick pools where primary phase multilaterals/drainholes have been drilled, drill secondary phase multilaterals /drainholes adjacent to lower pool boundary in respective pools) and use vertical flood from bottom to top taking advantage of the set up uniform pressure gradient.

(9) Produce the pools with constant pressure injection and constant pressure production mode upto the end of secondary/tertiary phases.
It may be noted that 10-15 vertical wells over the total plan areal extent of vertically extending set of pools and all horizons multilaterals /drainholes (in thick pools) will have to be completed before the first start of Confidential ' ~ Ashis Kumar Das, 2001-2002 production which is one disadvantage of the strategy (as revenue earnings are delayed) but this may not be all too prohibiting in long run, especially if long radius drainholes (1000-4000 ft) are feasible, which promises overall drilling cost reduction significantly and overall revenue increase as well, via expected large %OOIP recovery. Also, the use of multiple drainholes at a single elevation will add to production rate enhancement (b) special features for heating/miscible injection facility details This will be given in the final post-examination amended version of the patent application. This will include details of plant designing sections including separation of nitrogen from air, mixing separated gas from oil.and mixing additive (if required) for MMP lowering for nitrogen injection and placement of gradiented heating elements in thermal/electric/electromagnetic/microwave applications, such as E(s,t) or H(s,t) mode of placement. This very potent method requires more time than is normally possible for an independent inventor (requiring finance) and is therefore being filed for international coverage with all the detailed papers' listing (attached with the application) to establish priority on basis of basic filed application in India and all prior art (segmented arts in prior papers, published/unpublished, but not totally enabling prior disclosure of the entire process ) papers composing the final process.
V. Some Technical Roadblocks and Extended Special Applications Following are some yet to be removed technical road blocks of the method:
(a) Dipping Pools: Accurate placement of multilaterals in dipping pools and additional effect of dip and gravity on post-primary isobar and related control must be assessed. Reservoir modelling with optimization technique for objective function of near piston-displacement profile (or even flood front) may be loked into.
(b) Aquifer-supported Pools: In case of aquifer adjacent to pool(s), pool boundary segment that is aquifer supported must be accurately detected from reservoir engineering tools) such as well tests etc. Depending on dip of aquifer-pool system, and the pressure gradient existing in the aquifer and pool side(s), appropriate injection wells can be placed to enable advancing the aquifer pool contact region towards pool interior and through to the other end. From this discussion, it appears that pools with aquifer support will be better exploited with advancing of the contact right from the beginning of the primary recovery period.
(c) Current Technique Deficiency in Pool Shape/Size Determination by Well Test : This issue and its remedy have been discussed in several earlier papers although both the recognition of the deficiency (non-uniqueness of boundary details interpretation) and the proposed remedial techniques of removing non-uniqueness is still pending. The size of pool, however, can be determined from RLT but the shape determination by well tests still falls short of accuracy / uniqueness as demonstrated in these papers.
Hopefully, other alternative methods, such as seismic, will be made available to achieve this.
(d) Production Rate Enhancing: This will obviously require increased number of wells but, in initial assessment, the total number of wells required will still be much less than that commonly required in conventional spot patterned developments associated with water flood or aqueous FOR methods. An analytical and numerical investigation is currently under study.
(e)Application of the Concept to Heavy Oil Recovery: From preliminary assessment it appears that this concept of vertical flood using design of a "favourable" post primary recovery phase pressure distribution can also be extended to thermal recovery of heavy oil by "electriclthermal heating" method. Fig. 5 shows an approximate schematic of the idea which will require input (under study) for refinement of efficiency and feasibility assessment. First a convective heating /displacement assisted primary recovery (i.e. oil particle flow under both viscous pressure and convective displacement) using two stacks of wells and then again a convective heating (displacement assisted vertical flood with steamlhot water injection carried out from bottom to top set of wells (as shown in Figure 5 in details) will comprise the basic technique. As shown in bottom segment of Figure 5, use of held temperature/electric potential gradients using heating Confidential ~ Ashis Kumar Das, 2001-2002 surfaces over span lengths of the drainholes /multilaterals/horizontals will ease the pool wide convective heating and displacement because of large surface area of heat flow (more so with smaller dip of pool).
Particularly, with arrangement of "different (in magnitude) held gradients of electric potential" along each horizontal or multilateral span length a very effective intimate reservoir or pool wide heating can be effected with potential application of such heating applied to even tar sands recovery (e.g. Athabasca tar sands). The detailed economics of such "gradient" heating over long time, for particularly the applications such as million centipoise viscosity oil reserves such as Athabasca tar sands, is under current study but the intimate heating means which was missing in all earlier heating methods for thermal recovery has been successfully conceived in this work.
(f) The technical difficulty in accurately placing the multilaterals in the pools with technical limits on span lengths is being currently investigated.
(g) Another major roadblock of the method appears to be the requirement to invest a lot on complete set of drilling of the vertical wells and the drainholes over the field comprising a set of pools and then starting primary recovery which delays the revenue earning. This is being planned in the final amendable version of this application.

Vli. Prior Art References from Appficant/Inventor's Works (1) Das, A.K.: "Generalized Darcy's Law with Source and heterogeneity Effects", Journal of Canadian Petroleum Technology; Jan;1999 (2) Das, A.K.: "A Truly Chemical Theory for Polymer Flood: Applications", unpublished copyrighted in India and Canada a Confidential ~ Ashis Kumar Das, 2001-2002 (3) Das, A.K. : "Vertical Flood for Improved Recovery : A Concept", in a copyrighted (in Canada) unpublished volume titled Some Advanced Concepts in Petroleum Engineering and Re&rted Applications (4) Das, A.K.: "Commercial Feasibility of Vertical Flood: More Insights" in a copyrighted (In Canada) unpublished volume tiled Some Advanced Concepts in Petroleum Engineering and Related Applications (5) Das, A.K.: "A Proposed Paradigm Shift Approach to Oil Field Drilling/Production Strategy for Improved Economics", in a unpublished but copyrighted volume (in Canada) tiled Some Advanced Concepts in Petroleum Engineering and Related Applications (6) Das, A.K.: "Some Proposed Corrections to Petroleum Engineering Research in Near Future", ONGC Bulletin, vo1.33, no.l, June,1996 ********************
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Claims (8)

1. Vertical flood than conventional horizontal flood is better for improving displacement rate despite adverse vertical permeability

2. Multilaterals used profusely in the manner shown in Figure 5 will reduce drilling cost significantly over that by conventional mostly vertical and spot pattern based recovery

3. A simple draining concept based on from bottom to top flooding from primary recovery stage will allow simple unidirectional (bottom to top) isobar designing that will eliminate viscous fingering effect significantly in subsequent draining with / without water flood

4. The method proposes water flood devoid procedure but methodology for water flooded pools is also prescribed

5. A new improved heating method based on potential gradient placement of thermal/electric/electromagnetic/microwave potential(s), and a miscible flood method based on preferably nitrogen (or carbon dioxide or other) gas and additive (to lower minimum miscibility pressure) have been achieved pending detail ecnomics calculations after initial examination and amendment suggestions

6. A gas recycling (methane separated from production stream right from beginning) with increasing amount of nitrogen (or other gases mixed) is claimed to replace vacated oil pore space in the reservoir at end of recovery for prevention of subsidence and converting the oil reservoir as a nitrogen (or other gases) storage reservoir thus possibly enabling economics of complete sweeping of OOIP (original oil in place). Cold gas injection will reduce pump pressure costs as compression available from heating of cold gas from injection temperature to reservoir or any net final temperature in the oil bed(s) will be available.

7. The method will be applicable for recovery of all types of oil of light oil to one of viscosity of the order of million centipoises

8. An assessment is claimed to allow production of hydrocarbons as clean hydrogen and carbon dioxide gases in future