Vying In Cambrian Shale Reservoir Characteristics And Selection Evaluation Method Research

Along with the increasingly prominent contradiction between supply and demand of energy, oil and gas exploration and development fields gradually towards the direction of coalbed methane, shale gas and other unconventional oil and gas development. The lower Cambrian Qiongzhusi formation and the lower Silurian Longmaxi formation have two sets of high quality marine source rock in Weiyuan of Sichuan Basin. Recent years, several exploratory wells for shale gas in changling-weiyuan block, PetroChina, have been gained industrial air contionously, and it shows the wide exploration foreground of the shale gas in the lower palezoic, southern sichuan basin. Thereinto, the shale of the cambrain has not been explorated very much, and there is a potential for futher exploration. This paper is entitled by " Vying in Cambrian shale reservoir characteristics and selection evaluation method research ", and it takes the organic geochemistry 、the sedimentology 、and the reservior chracteristics researching to study the shale’s reservior chracteristics of the cambrian in the explorating area systematicly, establish the evaluation index which apply to the area, and use the Fuzzy similarity choice methods to evaluate the favorable area comprehensively.Through the compositive analysis with the core observation and well-logging data, we can see that Qiongzhusi Formation in Cambrian, Changling-weiyuan block, it is the muddy continental shelf facies, of the neritic shelf. The layer’s deposition is steady and a shallow depth, so the thickness of the effective shales with a stable distribution is large, and it’s benefical to save the shale gas.The organic carbon content in Qiongzhusi Formation ranges from 1.65% to 2.85%, and an average level is relatively high to 2.15%, which reach the lower limit of the organic carbon abundance, and proved to be preferably hydrcarbon source rock. On the other hand, the vitrinite reflectance(R0) here ranges from 2.2% to 4.4%, most of them are 3.2% to 4.4%, and changes in plane show to be lower in northwest while higher in southeast. For example, the maturity around the Mingshan-Leshan- Weiyuan block is relatively low from 2.2% to 2.6%, while the Naxi area in southeast is higher from 3.2% to 4.4%, the type of the organic matter in Qiongzhusi Formation is mainly Ⅰ,and rest are Ⅱ1. And the thermal evolution have been reach the stage of over-maturity.By shale argon ion polishing wafer environmental scanning. We can find that duing to the influence by the intensity compaction and thermal evolution, the shale’s pore is mainly inorganic and rest are organic, somewhere developes the microfracture. The pore lacunarity in Qiongzhusi Formation is average round by 2.85%, contempopary the brittle minerals are all high more than 40%, which is in favor of the late fracturing. The study for well-logging and mud-logging shows that the shale’s gas-bearing is preferably, and the shale gas wells contribute the industrial air, the microfracture is the primary flow channel.The distribution of the shale gas is mainly controled by the shale, which can reservoir forming in a row. Due to the difference from the hydrocarbon generation 、reservior and the storage conditions, the whole block can be separated to several ones, and the enrichment of the gas is also variant. Direct at the marine shale’s geological information in south central basin when explorating begins, basic on the master reservior forming factors, establish the evaluating index and standards for the shale gas’ explorating block, put forward the comprehensive evaluating methods for the favorable eletoral district potimizations.The reliability of the shale gas’ evaluating results, not only depend on theawaren ess of the organic carbon content, the lacunarity and the brittle menerals, but also the rationality of the evaluating index values and the weights, the selection of the favora ble district is lying on the generating ability,the reservior ability and the product cond itions.The roution studys applied to the electoral district evaluating, such as point syste ms, although simple priciple and convenient application, but also have some remarka ble shortcomings. For example, there is homogeneity between the evaluating index v ariation ranges and the evaluating standard. What’s more, among the evaluating grad es, there may be mutability. Direct at the various factors’ uncertainly and particular c omplexity which influence the shale gas’ electoral district evaluating, use the fuzzy si milar theory to calculate the evaluating area index values and the similarity coefficient between the favorable area, relatively area and the unfavorable area. The actual calc ulating examples show that the fuzzy similar theory could overcome the shortings co mpared with the routine studys, which have a high operability when counting and cou ld improve the reliability of the shale gas electoral district results.