Heavy Oil Potential Evaluation And Optimization Of Development Methods In The West Of Daqing

Heavy oil reservoir have characteristics with big resource potential and wide distribution area in the west of Daqing, mainly gathered in the west slope belt edge of Songliao basin, various types of reserves that has been submitted is 4372.3×104t, it is a important block for maintaining high and stable productivity in Daqing oilfield, which keep encouraging prospects. This paper is based on the actual problems of heavy oil reservoir in the development, on the basis of summing up predecessors' achievements, potential evaluation and the optimization of development methods for heavy oil in the west of Daqing are presented to provide some theoretical basis and available technology for high efficient development of Daqing oilfield based on organical integration of oil and gas field development geology, reservoir engineering principles, physical simulation experiment and reservoir numerical simulation, mainly completed the following research work:We start from the regional geology and evaluation of static and dynamic factors of reservoir formation, the distribution of oil, gas and water, the sources of heavy oil, migration pathways and accumulation patterns are analyzed. Unconformity surface is the main pathway of oil and gas transverse migration, though faults are not the main pathways of oil and gas migration, they can connect sand body and become the pathways of oil and gas lateral migration. When oil and gas meet favorable accumulation conditions, they can be gathered in formation, thus favorable oil and gas blocks such as Talahong, Pingyang, Alaxin, Erzhan, Jiangqiao and Fula Erji etc are formed. Analyzing deeply the oil, gas and water distribution rules of every reservoir provides scientific basis for making development scheme. Through analyzing hydrocarbon-generating conditions and components contrast of heavy oil in the west slope area, it is indicated that the most crude oil of west slope area is not autogenous, but the product of distant migration. The gentle slope belt of structure has a control function on oil and gas accumulation. Structure, lithology and the matching relation of faults etc can joint control hydrocarbon accumulation. It's concluded that main controlling factors of accumulation for heavy oil in the west of Daqing are:unconformity surface migration, fault ease, oil control of gentle slope and composite control of reservoir.The reservoir evaluation of western slope area is difficult, mainly showed in two aspects: in reservoir distribution, it presents that transverse variety of reservoir is big, sand body development is discontinuous and objective stratum is onefold; in reservoir type, it presents the increase of structural lithologic and lithologic reservoirs. Through dissecting losing Wells and synthesizing deposition, structure and accumulation characteristics, target suggestions of advantageous area for the main Saertu and Gaotaizi reservoir in the west slope area of Daqing are put forward. Through analyzing the geology of losing Wells and high-yield wells, favorable reservoirs are formed only when structure, sand body, reservoir are matched organically. A set of new methods for analyzing and seeking oil in blank area, extension area, the redevelopment area of remaining oil (encryption area) in the west of Daqing are formed. Applying multiple technologies such as seismic interpretation, reservoir prediction, sedimentary facies and fine sand anatomy, the approach of sub-blocks and sub-reservoir selection is carried out step by step under the guidance of main controlling factors of accumulation. With the multiple controlling factors of accumulation such as the structure, reservoir, reservoir fluid distribution etc, the potential for heavy oil resource in the west of Daqing is evaluated, geological reserves of A Laxin area, Erzhan area, Pingyang area and Jiangqiao area is estimated.Indoor experiments are done with the natural core of heavy oil block in the west of Daqing oilfield for optimization of different development methods. Various displacement experiments such as hot water flooding, steam flooding, chemical flooding, foam flooding, flue gas drive, microbial flooding etc are launched in order to optimize different development methods by parameter comparison and analysis of each displacement methods such as moisture content, recovery,injection pv, injection time and injection concentration etc. Experimental results show that the ultimate recovery of steam flooding and hot water flooding is highest, can be up to 50～70%; followed by CO2 foam flooding and surfactant chemical flooding, can reach more than 40%; however, the ultimate recovery of alternate flue gas/sewage and microbial flooding is relatively low.In view of characteristics of shallow buried depth, low reservoir temperature, small reservoir thickness and low production level of vertical cold production in jiang 55 block in the western slope of Daqing, so the preferable methods of developing the reservoir are horizontal cold production, horizontal steam stimulation and horizontal steam flooding. For different development methods such as horizontal cold production, horizontal steam stimulation and horizontal steam flooding, CMG numerical simulation software based on three-dimensional geological modeling are utilized to carry out history matching and predict their respective development effects by changing parameters such as horizontal length, reservoir thickness, well spacing, initial oil saturation, the quantity of cycle steam injection etc, development methods and production parameters are determined by comparing production effects. Simulation results indicate that oil producing rate and recovery percent of cold production are very low, advisable horizontal length of cold production is 700m; horizontal length of horizontal wells is 300m when the overall effect of steam flooding and steam stimulation is better; steam quality is 0.4 at least; the effect is best when steam flooding is performed after three stimulation cycles; for both cold production and thermal production, the bigger the well spacing is, the lower the recovery percent is; the thicker the oil reservoir is, the higher the recovery percent is. Economic evaluation in jiang55 block in the west of Daqing show that economic benefits of thermal recovery for horizontal well are significantly more qualified than cold production; net present value of Steam flooding is the largest in the case of high oil prices; internal rate of return of steam stimulation is the highest; the thicker the oil reservoir is, the better the economic benefit is.