Advanced Materials Research Vols. 734-737

Abstract: CO₂ storage in oil reservoirs is an important method to reduce Greenhouse Gas Emission. It was proven to have a great CO₂storage capacity and economic potentials via EOR by injecting CO₂into oil reservoirs. In China, most oil reservoirs went through waterflooding, and have high water saturation at present. The storage capacity in these oil reservoirs can be estimated on base of material balance method which considers the volume of displaced water and oil, CO₂ sweep efficiency, and CO₂ solution in oil and water. Case studies of four reservoirs selected from Xinjiang oilfield in China are conducted, the theoretical storage capacity and effective storage capacity is estimated. The results show that oil reservoir can provide much larger storage capacity, and oil and water displacement and CO₂dissolution in remaining oil and water are the main forms of CO₂storage in oil reservoirs after waterflooding. It’s a great option to inject CO₂ into these reservoirs to reduce Greenhouse Gas emission, and the detailed storage capacity is worth further studies.

Abstract: Figuring out the rule of remaining oil distribution after polymer flooding is the basis for continuing study on development policy after polymer flooding in Daqing Oil Field. Based on the basic principles of percolation mechanics, percolation mechanics of polymer flooding reservoirs under fixed injection pressure and injection rate was studied, the mechanism of remaining oil changes after polymer flooding was investigated; According to the numerical simulation results, the rule of remaining oil distribution in Daqing oilfield has been given out. This will be theoretical and practical guidance for enhancing oil recovery after polymer flooding.

Abstract: CBM resource in Huhehu depression Hailar Basin is large. Damoguai formaiton is the most favorable exploration coalbed methane target layer for top depth of 500-1200m, big coal seam thickness, low seam mineral content and high vitrinite by drilling, seismic and experimental data. Then cover character is evaluated and distribution is predicted. By analogy other low-level the CBM reservoir control factors, the south of depression is the most favorable area of CBM exploration for bigger coal thickness and better sealing conditions.

Abstract: During polymer flooding, certain amount of polymer would be lost. Polymer retention causes sweep volume expanding on one side, it also causes polymer loss on the other. Therefore, it is a very important topic to study the influencing factors of polymer retention. There are many factors affecting polymer retention process. This paper mainly studied the influence from dynamic factors such as polymer solution concentration, injection rate, injection time, injected pv number. This paper investigated the influence of these factors on polymer retention process, and optimized these factors to minimize polymer loss in reservoir.

Abstract: In gas drilling, hole-cleaning problem is serious due to formation water production when water layer drilled. Drill pipe sticking will affect seriously and drilling work cannot carry out. Therefore, formation water production is the most serious case. In this paper, we research that if formation water production is small, there are two migration model in annulus considering water absorption characteristics of cuttings when formation water production is greater than water absorption. One situation is the migration occurs under the condition that cuttings completely absorb the formation water. Another is cuttings and pure liquid migrate in the form of liquid droplet at the same time when cuttings do not completely absorb formation water. By using the minimum kinetic energy method, we consider the effects of gas influx under the two conditions and find that in most cases liquid carrying need more minimal gas influx than cuttings carrying. When formation water production is small in drilling work, increasing the amount of gas injection should used in order to ensure gas drilling safely and smoothly.

Abstract: Based on the Navier-Stokes equations for viscous, incompressible fluid and analytic relaxation approach, the 2-D numerical wave and current tank of the viscous fluid with constant depth is established, the volume of fluid (VOF) model is used to track the free surface for simulating the oil containment by rigid floating boom under wave and current conditions, and the motion of boom is accomplished by the technique of dynamic mesh. Then the variation of the oil shape under pure current condition, coplanar current condition and counter current condition were numerically studied, the effects of wave parameters on oil shape before boom were analyzed. The computed results are in general agreement with those obtained from previous studies.

Abstract: This paper, taking cumulative incremental oil production per unit thickness as evaluation index through variance analysis method, optimizes the injection rate and concentration of types of well groups with polymer flooding in the second-class oil-bearing layer of Daqing oilfield. The results show that for the ontocline and poorly communicated well groups, the optimal injection rate ranges from 0.10 to 0.15 PV/a and the optimal concentration ranges from 800 to 950 mg/L; for the supermature but poorly communicated well groups, the optimal injection rate ranges from 0.10 to 0.15 PV/a and the optimal concentration should be over 1200 mg/L; for the ontocline but well communicated well groups, the optimal injection rate ranges from 0.15 to 0.20 PV/a and the optimal concentration ranges from 850 to 950 mg/L; for the supermature and well communicated well groups, the optimal injection rate should be over 0.20 PV/a and the optimal concentration should be over 1100 mg/L.

Abstract: This page considers split methods on well group water injection rate researched by predecessors. So the dividing coefficient is introduced in determining the proper well group water injection. Based on considering all factors that affect the well group water injection, it analyzed the factors that were considered in the course of determining well group split coefficient. It adopted BP neural network method to determine well group split coefficient. Choosing the development data of one year, it established the neural network model about split coefficient and other values to determine well group split coefficient. Then it obtained the single well water injection rate.

Abstract: Oil industry at home and abroad has paid attention to the usage of horizontal well with the development of horizontal drilling technology, the number of horizontal well is increasing year by year inland, but some horizontal well constructions in thin oil pay is not ideal. Nanzhong 1H well has used double stepped horizontal well technology to develop thin oil pay, it has optimized the constructions in different stages and combined the steering technique in the drilling practice of thin oil pay, it has accelerated the drilling speed and reached the target fast and safely. It provides the reference for the further development of deep thin oil pay of horizontal well technology.

Abstract: Nowadays oil-gas exploration make a great contribution to the world oil-gas reserve increase. A series of deepwater passive continental margin basins are found in Northern Continental Slope of South China Sea. These basins consisted of thick Mesozoic and Cenozoic sedimentary strata with the characteristics of the major world deepwater oil-gas basins. As one of Cenozoic sedimentary basins in deepwater area of Northern Slope of South China Sea, Xisha Trough Basin developed 1500-8000m thick sedimentary strata, which are north-south zoning characteristics of thicker in the center and thinner both in the north and south sides of basin. In its evolutionary history there are two stages: One is Paleocene-Oligocene Rift with Continental River-Lake Facies sedimentary and the other is Miocene-Quaternary Depression with shallow sea-hemiplegic sedimentary. It has good petroleum geological conditions that source rocks consist of lacustrine mudstones, paralic mudstone, and marine mudstone, Tertiary high porosity and permeability deepwater fan reservoirs are the main reservoir, and structural traps and lithologic traps developed. In a word, it has good oil-gas exploration potential.