Characteristics And Evaluation Of The Organic-rich Shale Of Shanxi Formation, Southeast In Ordos Basin

Ordos basin is rich in oil and gas resources in upper palaeozoic, especially of shanxiformation, which is an important exploration of natural gas and unconventional shalegas horizon. The system research of shale gas reservoirs and sedimentarycharacteristics has a great significance to the enrichment regularity, nowadaysdomestic also has yet geology evaluation standard to continental, sea and landtransition phase of shale gas. Recent Shaanxi yanchang petroleum group cooperationwith the Ministry of land and resources, carried out the demonstration project ofdevelopment of shale gas in Southeast area of Ordos basin. China’s continental firstshale gas well-Liu Ping177had a successful fracturing gas production and success ofignition in ganquan in June2011In this paper, the study area is located in the southeastern ordos basin, the efficientlykey exploration area of shale gas demonstration project in yanchang oil in the district.Shanxi formation shale is well developed, and its total thickness up to100m, which asa marine-terrigenous facies coal-bearing rock series. This article has collectedcomprehensive information on the geological and logging of102oil and gas wells andhas completed the objective observation, sampling and analysis of cores of targetlayer of20resolution wells. Analyze the sedimentary environment of shanxiformation conditions of study area, and also the mineral composition, pore structure,adsorption, organic carbon content and other characteristics of organic-rich shalemore in-depth, discuss the reservoir characteristics and its main controlling factorsand the relationship between gas storage performance, and make a preliminaryevaluation of the favorable area of shale gas reservoirs in the study area. Results showthat: Overall performance of the Shanxi formation in study area developing land-seatransition phase delta on the basis of neritie continental shelf. Sedimentaryenvironmental conditions less salt water-in brine, water salinity changes repeatedlywith the influence of intermittent water. Shan2paragraph is more significantlyaffected by sea that its paleosalinity and Sr/Ba have more obvious relapse changefrom east to west and north to south. Paleosalinity and Sr/Ba ratio of Shan1paragraph have the trend of gradually reducing from east to west, demonstrates thatthe scale and degree of sea water influences are getting more and more weak, thepaleosalinity tends to be consistent. Mineral components of shale reservoirs consistmainly of clay minerals (kaolinite, illite, illite smectite mixed layer), as well assiliciclastic quartz, feldspar, small amounts of pyrite and siderite and other minerals.Average TOC content is3.98%and vitrinite reflectance is2.58%. Isothermaladsorption parameter is2.88m3/t on average. The average cumulative total porevolume of shale is0.0063ml/g. Pore structure types are mainly mesopores (average69.47%), with certain development of macropores (average28.03%) and slightdevelopment of micropores. Contents of quartz have a positive correlation with mesopores and macropores, while the situation is opposite for clay minerals. TOCcontents have a positive correlation with macropores. Clay minerals have a positivecorrelation with the adsorbed gas capacity, especially for illite. Saturated adsorptioncapacity increases gradually as the TOC contents enhance, and vitrinite reflectancealso have a positive correlation with saturated adsorption capacity. Saturatedadsorption capacity is positively correlated with micropore volume. Effective shalegas reservoirs of Shanxi Formation locate in southern Xiqiao Town, western regionsof Donggou, and the southern region of Zhangjiatan.