Granular-Polymer-Gel Treatment Successful in the Daqing Oilfield
- He Liu (Daqing Oilfield Co. Ltd.) | Hongxue Han (Daqing Oilfield Co. Ltd.) | Zhuling Li (Daqing Oilfield Co. Ltd.) | Bo Wang (Jilin Oilfield Co)
- Document ID
- Society of Petroleum Engineers
- SPE Production & Operations
- Publication Date
- February 2006
- Document Type
- Journal Paper
- 142 - 145
- 2006. Society of Petroleum Engineers
- 5.7.5 Economic Evaluations, 5.3.2 Multiphase Flow, 4.1.2 Separation and Treating, 5.1.5 Geologic Modeling, 4.6 Natural Gas, 5.4.1 Waterflooding, 5.1.1 Exploration, Development, Structural Geology
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Reservoirs in the Daqing oil field are complex-fluvial, lacustrine, and delta-deposited heterogeneous pay zones, with mixed porosities and various permeabilities ranging from several md to 1,200 md. Both vertical and horizontal heterogeneities are abundant. Conformance control for such reservoirs is difficult but of great importance. Recently, we used a method that employs injection of preformed gel particles to adjust the flow distribution of injected water.
This paper presents the technique that was used for the first time in a typical region in the Daqing oil field. The particles used in this project were preformed crosslinking granular polymer gels. Granule diameters were 1.5, 3, and 5 mm, which were bigger than particles used in other oil fields in China. Before actual treatment, numerical simulation was used to predict the pressure change during the process of treatment, the amount of polymer gel to be used, and the quantity of water to be injected. In actual treatment, the total injection was 3100 m3, which was injected in three plugs: pretreatment, main-plug injection, and seal-plug injection. The application proved successful. Economically improved oil production and reduced water cut were observed.
Reservoir heterogeneity, along with high oil-to-water viscosity ratio, causes fingering and/or water breakthrough along higher permeability layers when waterflooding an oil field. This in turn decreases the water-sweeping volume and waterdrive effect, making the medium- or lower-permeability layers poorly productive or even unproductive. Blocking higher-permeability layers with chemical reagents along the flow direction of water can efficiently increase the water-affected volume and adjust productive and absorptive sections of the reservoir. Therefore, if water cut can be decreased by blocking the high-permeability flow path in the fingering region, oil production will be increased.
In recent years, laboratory studies (Liang and Seright 1997) and pilot field applications (Alvarez et al. 2001) of preformed gel for conformance control have gained more and more interest. Coste et al. (2000) discussed a pilot test in Shengli oil field in China. In 1999, field application of preformed gel for conformance control was successfully carried out in another oil field in China (Bai et al. 2004a). The first pilot test in the biggest oil field in China—Daqing oil field, which will also be discussed here—was carried out in 2000.
Daqing oil field was discovered in a continental fluvial-delta sedimentary environment and features complex geologic conditions and high permeability contrasts. The north Xingshugang region is one of the most typical regions in the oil field. Most pilot experiments are carried out in this region. If any test or experiment is successful in the north Xingshugang region, it will be suitable for most regions in the oil field. For this reason, the north Xingshugang region was chosen as the pilot area for the preformed-polymer-gel conformance-control test.
Both domestically made polymer gels and imported polymer gels were investigated according to the geological characteristics and the behavior of reservoirs in the north Xingshugang region of the Daqing oil field. The physical and chemical properties were also compared and analyzed. In the end, the granular polymer gel discussed here was chosen.
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Alvarez, I. et al.: "WaterControl Experiences in the Motatan Field Using Specially Designed Gels ,"paper SPE 69545 presented at the 2001 SPE Latin American and CaribbeanPetroleum Engineering Conference, Buenos Aires, 25-28 March.
Bai, B. et al.: "PreformedParticle Gel for Conformance Control: Factors Affecting its Properties andApplications," paper SPE 89389 presented at the 2004 SPE/DOE Symposium onImproved Oil Recovery, Tulsa, 17-21 April.
Bai, B. et al.: "PreformedParticle Gel for Conformance Control: Transport Mechanism Through PorousMedia," paper SPE 89468 presented at the 2004 SPE/DOE Symposium on ImprovedOil Recovery, Tulsa, 17-21 April.
Coste, Y.L. et al.: "In-DepthFluid Diversion by Pre-Gelled Particles. Laboratory Study and PilotTesting," paper SPE 59362 presented at the 2000 SPE/DOE Improved OilRecovery Symposium, Tulsa, 3-5 April.
Liang, J.T. and Seright, R.S.: "Further Investigations of Why GelsReduce Water Permeability More Than Oil Permeability," SPEPF(November 1997) 2, No. 4, 225.