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Preformed Particle Gel for Conformance Control: Factors Affecting its Properties and Applications
Bai, Baojun (Research Institute of Petroleum Exploration and Development, PetroChina) | Li, Liangxiong (Research Institute of Petroleum Exploration and Development, PetroChina) | Liu, Yuzhang (Research Institute of Petroleum Exploration and Development, PetroChina) | Wang, Zhongguo (Daqing Oil Company Limited) | Liu, He (Daqing Oil Company Limited)
Abstract Injecting preformed particle gel (PG) as a fluid-diverting agent to reduce water production is an attractive new procedure designed to minimize some of the risks inherent in gel treatments based on in-situ gelling. The objectives of this paper are:understand how to control PG properties by changing gelant compositions and their fraction when synthesized; determine where PG can be applied and how reservoir conditions affect PG properties; and outline candidate well criteria and the proper injection procedures by illustrating several field applications. Based on laboratory experiments, the following results will show that:PG strength and swelling capacity can be controlled by adjusting gelant compositions; certain additives can improve PG stability at elevated temperatures (120°C); increasing temperature will increase the swelling ratio and the swelling rate of PG, and increasing salinity will reduce the swelling capacity of PG and will increase PG strength; the swelling capacity of PG is insensitive to pH; PG is insoluble in water, but absorbs it, swelling up to 20–200 times of its original size. It is strength- and size-controlled, environment-friendly and not sensitive to reservoir minerals and formation water salinity. Three examples from more than 200 operations were selected to show how to choose candidate wells and how to operate the injection procedures. PG can be used as a conformance control agent to correct permeability heterogeneity for those reservoirs with fractures or channels, both of which are widely found in mature water-flooding oilfields in China. Introduction Most oil fields in China were found in continental sedimentary basins. They are characterized by complex geologic conditions and high permeability contrasts inside reservoirs. To maintain or increase the driving force, these oilfields were developed by water injection. However, serious vertical and lateral heterogeneity of formations resulted in rapid water cut increase of production wells. Moreover, sand production and dissolution of rock matrix further worsen reservoir heterogeneity. Severe heterogeneity of reservoir has become one of the most important problems that reservoir engineers are facing. Many inter-well tracer tests have shown that channels or fractures widely exist in most oilfields, no matter whether they have fracture or not at their early development stages. In this paper, "channel" means an open, linear-flow structure. It does not mean flow through matrix. Another example of worsen heterogeneity comes from the application of clay gel in China Oilfields. Many injection wells have been successfully injected hundreds or thousands tons of clay respectively. If we calculate the permeability from Darcy law according to the "1/9~1/3 rules", which is a rule about how to match pore throat and penetration particle size, the formation permeability should be more than one thousand Darcy . Moreover, earlier polymer breakthrough in Daqing, Nanyan, and Shenli oilfields further proved channels or fractures are widely spreading in most oilfields. To control water cut and improve oil recovery of oilfields, many technologies, such as polymer flooding, surfactant flooding, foam flooding and so on, have been taken in China so far. One of the most popular methods is to inject gel to reduce flow capacity of channels or fractures and divert following fluid (normally, water) to unswept oil zones. [8,9] Before 1990's, gel treatment concentrated on correcting permeability heterogeneity near wellbore (normally 5~10meters). But in-depth gel treatment technology has become more and more important for oilfield owners because heterogeneity of thick net pay has become main problem influencing oil recovery of mature oilfields and gel has been injected multi-times in some wells respectively so that no remaining oil is left near wellbore.
- North America > United States > Texas (1.00)
- Asia > China > Heilongjiang Province > Daqing (0.25)
- Government > Regional Government > Asia Government > China Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (26 more...)
Preformed Particle Gel for Conformance Control: Transport Mechanism Through Porous Media
Bai, Baojun (Research Institute of Petroleum Exploration and Development, PetroChina) | Liu, Yuzhang (Research Institute of Petroleum Exploration and Development, PetroChina) | Coste, J-P (Research Institute of Petroleum Exploration and Development, PetroChina) | Li, Liangxiong (Research Institute of Petroleum Exploration and Development, PetroChina)
Abstract Preformed particle gel (PG) has been successfully synthesized and applied to control excess water production in some mature water-flooded oilfields in China. Investigations show that PG is strength- and size-controlled, environment-friendly, stable over long periods of time, and very likely capable of overcoming some drawbacks inherent in gel treatments based on in-situ gelling. Its thermostabilization is not sensitive to reservoirs minerals and formation water salinity. To support its future applications, this paper describes experiments that investigate the mechanisms for PG propagation through porous media. Visual observations in etched-glass micro-models demonstrate that PG propagation exhibits six patterns of behavior: direct pass, adsorption and retention, deform and pass, snap-off and pass, shrink and pass, and trap. Which pattern is dominant is related to the diameter ratio of swollen PG and pore throat, PG strength and the driving force. In macroscopic scale, PG propagation through porous media can be described by three patterns: pass, broken and pass, and plug. Which kind of pattern is dominant can be determined by pressure change with time at different tap, particle size of effluent and residual resistance factor at different segment of a core. Measurements from core-flooding and micro-model experiments show that a swollen PG particle can pass through a pore throat whose diameter is smaller than its diameter due to the elasticity and deformability of swollen PG. PG strength is a principle parameter to determine the diameter ratio of a PG particle and a pore throat that PG can pass through a porous medium. A PG particle can move through a porous medium only if a driving pressure gradient is higher than a threshold pressure gradient. The threshold pressure depends on PG strength, the diameter ratio of particle and average pore size. Further work will investigate the potential for PG to improve oil recovery and the optimization method to design PG treatments. Introduction Reservoir heterogeneity is a principle factor responsible for low sweep efficiency of injected water or gas. To control conformance in water or gas flooding, many technologies have been applied, such as polymer flooding, foam flooding, surfactant flooding and so on. Injecting large volumes of gel to correct in-depth permeability for those reservoirs with fracture or channel has become an attractive technology. In this paper, "channel" means an open, linear-flow structure. It does not mean flow through matrix. In recent years, the study of preformed gel for conformance control has gained more interest among gel-based enhanced oil recovery processes. Seright studied some properties of preformed bulk gel through fractures and proved that preformed gel had better placement than in-situ gel and could effectively reduce gel damage on low permeability unswept oil zones. Chauveteau et al. synthesized preformed microgels which were cross-linked under shear, and Feng et al. proved that the microgels could be easily injected into porous media without any sign of plugging and these micro-gels should be good candidates for water shutoff and profile control operations. PG is another kind of preformed gel in which bulk gel synthesized in surface facilities is cut into particles and is dried to form xerogel particle at a higher temperature. This process provides a product that is more easily packed and saves transport cost. Some advantages of PG can be summarized as following:PG, synthesized on surface facilities, can overcome some distinct drawbacks inherent in in-situ gelation systems, such as lack of gelation time, uncertainness of gelling due to shear, degradation, chromatographic of gelation compositions, dilution by formation water; PG is strength- and size-controlled, environment-friendly, and its thermostability not sensitive to reservoirs minerals and formation water salinity; PG can resist high temperature (120 °C) and high salinity (300,000 mg/L)
- Asia > China (1.00)
- North America > United States > Texas (0.47)
- North America > United States > Oklahoma (0.30)
- Government > Regional Government > Asia Government > China Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)