Title of Invention

A PROCESS FOR PREPPAIRING CROSSLINKED POLYMER GEL FOR WATER AND GAS SHUTOFF IN HIGH TEMPERATURE OIL WELLS

Abstract A PROCESS OF FOR PREPPARING CROSSLINKED POLYMER GEL FOR WATER AND GAS SHUTOFF IN HIGH TEMPERATURE OIL WELLS A process employing oraganically cross-linked and chemically catalyzed polymer gel system in high temperature oil wells for ihgher oil recovery and reducing water/gas production. A solution of a polymer, Hydroquinone and Hexamine as a crosslinker is prepared as a single aqueous gelant solution, The solution is injected in the target area from where unwanted fluids from gas zone above or water zone below the oil formation sand. Sealing the source of unwanted fluids allows deliverable pertroolum oil production from the oil-bearing sand relatively free from unwanted fluids.
Full Text FORM 2 THE PATENTS ACT, 1970
(39 of 1970) COMPELETE SPECIFICATION
[Section 10; rule 13]
A PROCESS FOR PREPPAIRING CROSSLINKED POLYMER GEL FOR WATER AND GAS SHUTOFF IN HIGH TEMPERATURE OIL WELLS
MEHRAM LAL PANWAR
INSTITUTE OF OIL AND GASPRODUCTION TECHNOLOGY OF OIL AND
NATURAL GAS CORPORATIONLTD
PANVEL, Navi Mumbai - 410221,Maharashtra, India,
INDIAN
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.




A PROCESS FOR PREPPAIRING CROSSLINKED POLYMER GEL FOR WATER AND GAS SHUTOFF IN HIGH TEMPERATURE OIL WELLS
The invention relates to an improved chemical system of water and gas shutoff in high temperature oil wells by using organically cross-linked gels system.
Petroleum liquids are stored underground in sandstone or limestone reservoirs. Wells are drilled to take out these petroleum liquids. Generally in reservoirs there are three types of fluids stored by nature i.e. gas, oil and water. Gases being the lightest are stored on top, oil in middle and water at the bottom in the reservoir. The production of unwanted water leads to both lifting and water disposal costs, add environmental concerns and reduces oil production. It also necessitates additional maintenance for production equipments and down hole treating for corrosion, bacteria, scale and naturally occurring radio-active materials. The total cost for handling and disposal of water is about 22 % of oil production cost.
To shutoff the unwanted water and gas from an oil well, the first step is to find out the exact source of water and gas. There are many diagnostic methods to ascertain the source of unwanted fluid comprising water and gas and their use also necessitate special well conditions. In the situation when unwanted fluid producing zone is somewhere above or below the oil bearing and producing formation and, unwanted fluid travels to the wellbore through micro channels, annuli, coning or cusping, it is difficult to stop unwanted fluid using conventional oil well cement due to its restricted penetration owing to the particle size.
Cement and micro-fine cement give temporary relief to some extent, but when there are repeated failures of cement squeezes, chemical methods can be used. The advantage associated with chemical & polymer methods is that they can be designed and placed deeper into the reservoir and unwanted fluid may not be able to circumvent it easily and long lasting results are obtained.
The present invention relates to an improvement replacing the use of conventional cement by a tailored polymer gel process for plugging the micro channels and annuli in the primary cement behind the well casing. The application of this chemical process does require identification of water source, isolation of zone and deployment of rig.
The present invention is described in the context of specific terms, which are defined as follows. The oil sand formation consists of a region where the formation volume is characterized as
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essentially homogeneous, continuous, sedimentary reservoir material. But this is inclusive of terms such as streaks, fractures, fracture networks, vugs, solution channels, caverns, washouts, cavities, etc.
The term "gel" as used herein is directed to a continuous three-dimensional crosslinked polymeric network having an ultra high molecular weight. The gel contains a liquid medium such as water that is confined within the solid polymeric network. The fusion of a solid and a liquid component into a single-phase system provides the gel with a unique phase behavior. Gels employed by the present invention have sufficient structure and strength so as not to propagate water and or fines from the confines of a plugged region above or below into a less permeable region adjoining the plugged region once in place.
The gel is qualitatively defined as "flowing" or "non-flowing" based on its ability to flow under the force of gravity when unconfined on the surface at ambient atmospheric conditions. A flowing gel flows under these conditions; a non-flowing gel does not. Nonetheless, both a non-flowing gel and a flowing gel are defined herein as having sufficient structure so as not to propagate from the confines of the desired treatment region when injected therein.
"Crosslinked to completion" means that the gel composition is incapable of further crosslinking because one or both of the required reactants in the initial solution are consumed. Further crosslinking is only possible if polymer, crosslinking- agent, or both are added to the gel composition.
The gel composition utilized in the present invention is comprised of a polymer named Partially Hydrolyzed Poly Acrylamide a commonly known as PHPA and a crosslinking agent capable of crosslinking the two polymer species. The PHPA referred herein should be a free flowing powder or bead polymer (free from lumps, dirt and foreign matter) with maximum of 15% moisture content. The PHPA polymer involved in the present invention is impregnated with sodium acrylate and Acrylamido-2-Methyl Propane Sulphonic acid commonly known as AMPS, which provides it the stability to withstand the degrading effect of the inorganic di and tri-valent ions and high temperature.
The crosslinking agent used in the present invention are a mixture of Hydroquinone and Hexamine in a proportion described below.
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The present process enables the practitioner to customize or tailor-make a gel having a predetermined gelation rate and predetermined gel properties of strength and stability from the above-described composition. The gelation rate is defined as the degree of gel formation as a function of time or, synonymously, the rate of crosslinking in the gelant solution. The degree of crosslinking may be quantified in terms of gel viscosity and/or gel strength. Gel strength of a non-flowing gel is defined as the coherence of the gel network or resistance to deformation under external forces. Gel strength of a flowing gel is defined as the resistance of the gel flow under gravitational force. Stability is defined as either thermal or phase stability. Thermal stability is the ability of a gel to withstand temperature extremes without degradation of its polymeric and/or crosslinking chemical bond. Phase stability is the ability of a gel to resist syneresis (separation of entrapped water), which can detract from the gel structure and performance.
Present invention has temperature limit of the gelation solution at the surface is the freezing point of the solution and the upper limit is essentially the thermal stability limit of the polymer and or 150°C restricted by the maximum across the well depth temperature. The solution is generally maintained at tropical ambient temperature at the surface. Increasing the temperature within the prescribed range at the surface increases the gelation rate and also, increasing the total polymer and crosslinker concentration increases the gelation rate and ultimate gel strength at a constant ratio of polymer to crosslinking agent.
The practitioner advantageously selects a predetermined gelation rate that enables preparation of the gelation solution at the surface, injection of the solution as a single uniform slug into the wellbore or the predetermined interval along the well depth, and displacement of the entire slug into the desired interval above or below the oil sand formation. Once in place at the desired treatment region, gelation of the solution advantageously proceeds to achieve substantially complete gelation of the solution in situ.
The present gelation mechanism enables the practitioner to design a gelation solution that can be injected into a treatment region at a desired injection rate with assistance to pre-achieved injectivity by a conventional mud acid placement. The solution is preferably gelled once it is in place in the desired subterranean region to minimize water movement thereby allowing formation fluids; water, oil and gas to the well bore from shut in production wells. The gelation time of the gel ranges from 4 hours up to 48 hours or longer for both flowing and non-flowing gels.
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Both flowing and non-flowing gels can be used for treatment of high permeability zones of the matrix because in general neither will flow from the treatment zone upon complete gelation, a necessary condition for the present invention. However, non-flowing gels as of our invention are often preferred for treatment of high permeability zones producing undesired water and gas in direct communication with production wells because of their increased strength.
The gels are produced in a manner, which renders them insensitive to most extreme formation conditions. The gels can be applied to the treatment of many different geological structures including high permeability zones within the formation oil sand. The gels can be stable at formation temperatures as high as 150°C. The gels are relatively insensitive to the stratigraphy of the rock and can be employed in carbonate and sandstone strata and unconsolidated or consolidated strata having varying mineralogy. Once the gels are in place, it is extremely difficult to displace the gels by physical or chemical means other than total destruction of the crosslinked network.
The following examples demonstrate the laboratory test practice and utility of the present invention but are not to be construed as limiting the scope thereof.
Process Verification
The invention will now be described in more details with reference to its formulation to be used in blocking the water from oil sands.
This gel system comprises of a PHPA polymer and two organic crosslinker having the following components.
• PHPA polymer-Alcoflood 251-S
• Hydroquinone
• Hexamine
The gel developed by the combination of these chemicals is suitable for sand stone formation having the following properties
• Low initial viscosity but forms strong elastic gel to withstands high differential pressure.
• Long term stable at up to 150 °C.
• Unaffected by high salinity
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• No effect of pH o gelation rate or gel stability in the pH range of 5 - 9
• Gelation reaction start above 80 °C i.e only after injection into the well bore and does not form gel at surface condition.
• Gel timing can be tailored depending on operational requirement.
Application
The polymer solution forming gel has viscosity in the range of 2 to 200 centi Poise at surface and can be applied to seal off the channels behind casing and formation zones producing undesired fluids. Polymer solution squeeze can be carried out by prior protecting the oil producing zone duly protected by cement squeeze, the target section will then be opened by perforating the casing with special purpose gun. Then efforts will be made to establish injectivity with 1% KCl brine solution. If successful, the polymer gel will be pumped otherwise a acid job can be performed to establish injectivity.
After the squeeze of polymer and giving due setting time, the well will be available for final completion.
This polymer gel is a three-component chemical system having temperature and concentration sensitivity. Carried out optimization studies by using laboratory grade chemicals with the aim to evaluate optimum chemical compositions, gel setting timings and gel strength
Chemical Compositions:
All the three chemicals viz: Polymer Alcoflood-251-S, Hydroquinone (HQ) and Hexamine (HA) were tested with different concentration combinations and inferred the proportions in the treatment solution.
Polymer Alcoflood 251S - Polymer concentration was worked out to be 3 to 6 %
depending upon injectivity constraints.
Hydroquinone - Hydroquinone concentration was worked out to be 0.6 to 8% as suitable to 3 to 6 % polymer concentration.
Hex-amine - The concentration of Hexamine was tailored to 0.8 - 1.0% commensurate to the Hydroquinone concentration of 1 % as and 3 to 6 % of polymer concentration.
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Composition Chemicals Concentration Remarks
Composition-A Polymer
Hydroquinone
Hexamine 3%
0.6%
0.8% Flowing gel of viscosity range 2-5 CP
Composition-B Polymer
Hydroquinone
Hexamine 6%
0.8%
1.0% Non-flowing gel of viscosity range 30-40CP
Gel Setting Time:
Gellation studies were carried out with above compositions at 80°C, 90 °C, 100°C, 110°C, 120°C, 130°C, 140°Candl50°C.
Following were the gel setting timings were observed:

Temperature Gel Setting Time Composition-A Gel Setting Time Composition-B
80 °C 132 Hrs 84 Hrs
90 °C 98 Hrs 69 Hrs
100°C 36 Hrs 29 Hrs
110°C 31 Hrs 22 Hrs
120 °C 25 Hrs 16 Hrs
130 °C 19 Hrs 14 Hrs
140 °C 16 Hrs 12 Hrs
150°C 11 Hrs 9 Hrs
All the above setting timing was found to be normal in line with the job execution sequencing.
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CLAIMS
I Claim:
1. A process for preparing cross linked polymer gel for water and gas shutoff in high temperature oil wells, having bottom hole temperature 100 to 150 °C. gel prepared by mixing polymer - Alcoflood-251 S - 3-6 % , hydroquinone from 0.6 -8% and hexamine 0.8 -1% in water as solvent and injecting the said polymer-chemical composition gel at bottom hole to form cross linked polymer network in the form of a semi solid material.
2. The process as claimed in claim 1 wherein said cross linking is quantified in terms of final gel viscosity.
3. A process constructed, and arranged substantially as herein described.

Dated this 18tn day of August 2004
MEHRAM LAL PANWAR

Documents:

897-mum-2004-abstract(24-12-2007).doc

897-mum-2004-abstract(24-12-2007).pdf

897-mum-2004-cancelled page(24-12-2007).pdf

897-mum-2004-claims(granted)-(24-12-2007).doc

897-mum-2004-claims(granted)-(24-12-2007).pdf

897-mum-2004-correspondence(ipo)-(17-1-2005).pdf

897-mum-2004-form 1(19-8-2004).pdf

897-mum-2004-form 19(19-8-2004).pdf

897-mum-2004-form 2(granted)-(24-12-2007).doc

897-mum-2004-form 2(granted)-(24-12-2007).pdf


Patent Number 213178
Indian Patent Application Number 897/MUM/2004
PG Journal Number 04/2008
Publication Date 25-Jan-2008
Grant Date 24-Dec-2007
Date of Filing 19-Aug-2004
Name of Patentee MEHRAM LAL PANWAR
Applicant Address PANVEL, NAVI MUMBAI 410 221
Inventors:
# Inventor's Name Inventor's Address
1 BISHWESWAR GHOSH M-301, RAILVIHAR CO.OP.HSG.SOCIETY, SECTOR-4, KHARGHAR NAVI MUMBAI-410210
2 BHAGWABN DASS BANSAL 202, MURARI EKTA, PLOT NO-1920, SECTOR-4, KHARGHAR NAVI MUMBAI -410210
3 RANJEET KUMAR ANAND B-1003, RAVAL TOWER PLOT NO-16 SECTOR 11, CBD BELAPUR NAVI MUMBAI-400614
4 SHIV CHARAN SINGH B-505, MARUTI PARADISE, SECTOR-15.CBD BELAPPUR. NAVI MUMBAI-400061
5 BISHNU DEO SINGH B-3-12-467. ONGC COLONY, PANVEL-410221. DISTRICT-RAIGAD.
PCT International Classification Number C09K 8/50
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA