The Trade-off Study On Evaluation Criterion Of Domestic And External Shale Gas

With the increasing of energy demand and the continuous consumption of the conventional oil and gas resources, the supply and demand between Oil and gas have become increasingly prominent. Therefore, coalbed methane, tight sands gas, volcanic rock, shale oil and gas and other unconventional energy become more and more important, and oil and gas explorationists are attention of it. Exploration and development in the United States revealed that the momentum of development and the fastest potential this year was undoubtedly the shale gas in unconventional oil and gas. Shale gas occurs in the organic-rich shale with adsorption and free phase, and has a commercial value of biogenic and thermogenic unconventional gas. From exploration and development of the global renewable energy analysis found that Shale gas is one of the most realistic conventional oil and gas resources to succeed.In china, most of the Basin have the basic geological conditions for shale gas exploration, various geological history, organic-rich shale formations are well developed. However, exploration and development of Shale gas is vary late, because of the special geological conditions, including burial depth deeper, stratigraphic older, post-tectonic deformation. This determines that the Evaluation criteria and exploration experience of the North American shale gas may not be fully suitable for the evaluation and exploration of shale gas in China. In order to improve the success rate of shale gas exploration, at present, we need to study and establish the evaluation criteria be appropriate for China’s geology practical shale gas constituency, avoid evaluation in the constituency, compare our shale with the North American shale in Geochemical parameters and reservoir parameters. We should give full consideration to the particularity and complexity of China’s shale gas formation. In terms of late transformation of a strong shale gas in the Paleozoic of southern China, in addition to carrying out routine evaluation of research, we should strengthen research on storage condition about it.Shale gas and conventional gas have a significantly different in gas-rich reservoir control factors. Shale gas reservoir forming characteristics:self storage; reservoir early; traps; the low porosity and permeability of the reservoir; the diversity of gas existing state; shale gas is easier to preserve; symbiotic coexistence with conventional oil and gas. The gas-rich reservoir control factors of shale gas to studying content currently, including Organic carbon content; thermal evolution extent; Porosity and permeability Features; Mineral composition and the effective thickness and so on. Correctly evaluating these parameters plays a great significant role in rational assessment of shale gas reservoirs. Evaluation criteria and exploration experience of the existing shale gas may not be entirely suitable for the evaluation and exploration of domestic Basin shale gas. These evaluations are based on the analysis of existing Basin shale gas data, shouldn’t exclude the particularity of the study area. For different Shale basins, even with a different area of the same set of shale, there may be differences, so Shale gas evaluation criteria to be further Verified and revised.According to the basic conditions of the petroleum geology, the formation of any hydrocarbon reservoirs must have three key elements, Oil and gas sources, Storage space and storage conditions. Shale gas is no exception, the first condition is hydrocarbon generation, Shale gas source rocks is asphaltenes or the dark of organic matter, black or high-carbon shale, organic matter content, a high degree of thermal evolution, Kerogen type is good and so on. Followed by the characteristics of the reservoir, including porosity and permeability characteristics and mineral composition, the low porosity and low permeability of shale, fracture development will improve the content of the shale porosity and permeability capacity, brittle minerals such as quartz has an important significance in Shale brittleness and in guiding the post-development; Again is the storage conditions, Shale gas form edge as well as occurrence gathering, needn’t to structure the background, for the subtle trap gas reservoir, faults and macroscopic cracks play the destructive role, the intense tectonic activity is not conducive to the preservation of shale gas.In this paper, on the basis of systematic investigating the North American shale gas reservoirs Research, from several main parameters of gas assessment the start, combined with the domestic two representative shale gas prospect area-the Weiyuan lower Paleozoic marine shale and lacustrine mudstone in Songliao Basin Gulong Qingshankou. For total organic carbon content, Ro, Effective thickness, Clay mineral content, Porosity and permeability and the present depth and so on. Take full account of matching relationship among a variety of geological parameters in basin.Get the similarities and differences and gaps of Evaluation criteria in three Represents regional, provide a theoretical basis for better evaluating domestic shale gas resources.U.S. shale gas basin tectonic stability, flat strata, the depth of Gas shale burial is Moderate (1000-3500m), vitrinite reflectance (Ro) is greater than0.4%, the total organic carbon content is generally0.4%to2%, Kerogen have type Ⅱ and typeⅢ, a variety of pore development (porosity of2%to10%, concentrated in the4%to5%), the Ultra-gland layer, the rate of Penetration less than0.1×10-3μm2, Shale brittleness is good, Minimal cracks of tectonic fractures are well developed. Our country has the potential of shale gas basin strata where the geological conditions of the basin. Sichuan Basin’s Paleozoic belong to a marine sedimentary basin, Shale’s deposition environment is deep-water deposits, shallow-deep-water shelf facies. The main layers is the Lower Cambrian and Lower Silurian, the thickness of Shale is200-400m, the depth of burial about3000-4000m, Ro distributed in1.1%to4.6%, the TOC is greater than1.0%on average, Kerogen type is Mainly Ⅰ-type, fault activity is relatively strong and fracture development, Songliao Basin is a Large Mesozoic and Cenozoic in eastern China which has a dual structure of the broken Au composite sedimentary basin. The Gulong located in the west of the Central depression area of the northern Songliao Basin, a long-term development of Inheritance of depression, the major group of Qingshankou is lake sediments, Shallow lake-deep lake mudstone’s thickness is150～500m, the content of total organic carbon is generally1.5%to2.1%, Ro is1.1%to2.0%, Kerogen type is Mainly I-type.