The Sedimentary Microfacies Research Of The Reservior Of He8Member In The Southern Zone Of Sulige Area

Located in northern Ordos basin, with Carboniferous and Permian gas-bearing horizon,Sulige gas field has He8member as one of the main production layers in this area, and thedetailed study of its depositional microfacies has significant in the laws of reservoir forming aswell as the exploration and development of hydrocarbon. With He8member in the southernpart of Sulige gas field as study subjects, this paper is a comprehensive and in-depth study ofthe reservoir characteristic, provenance characteristic and the characteristic of the wellcorrelation facies etc. with sedimentology, sequence stratigraphic and analysis of data fromlogging well as well as core porosity and permeability.Study showed that He8member which formed in Upper Paleozoic of Sulige gas field canbe divided into2long sequence circles(LSC1,LSC2) and4middle sequencecircles(MSC1-MSC4). The deposition environment of He8member is braided river delta thatcan be divided into foreland delta subfacies and plant delta subfacies. These subfacies havedistributary channel, estuarine bar, estuarine depression microfacies etc. Influenced bydifferent provenance which coming from northern west, north and northern east, the content ofquartz, debris and heavy minerals has significant differences.In conclusion of the results above, the Upper Paleozoic Lower Shihezi Formation He8member is divided into foreland delta and plant delta vertically, located behind the plant deltafacies belt. The sedimentary frame-sands are distributary channel and underwater distributarychannel; the sand body distributes in north-south direction and shows fine connectivity,however, the horizontal connectivity in east-west direction is worse as a whole part,distributing dominantly in bonded shape in north-south direction, meanwhile, forming somepotato-like shape and irregular shape sands. Based on gas testing results and core analysis data,it shows that the porosity and permeability in gas wells are in positive correlation with gasproduction rate, which means reservoir quality has obviously control on the distribution of thegas wells. The relationship in gas production rate with porosity and permeability of gas-waterwells showed different performances in different layers, which means the distribution of thegas-water wells are topo-controlled by reservoir quality microcosmically.