The Reservoir's Characteristics Of H2+3 In Lower Shihezi Formation In Shiguhao Area

The tectonic setting of area of Shiguhao is located in step-fault zone of Hangjinqi, which is in north of Erbei-Yimeng upheaval. There are two first-level units in area of Shiguhao, which is widespread nosing structure of and several small tectonic uplifts of upheaval which of them is declined down towards the southwest, in south of which is Yi-Shan slope and north of which is YiMeng upheaval. The reservoir type of gas reservoir is a typical gas field with low porosity and permeability in the place in which with low degree of exploration and the reservoir vary in a deeper range. So to make the most of geological data and well-logging information is the important means to comprehensive research reservoir assessment in this area.The research area is located in northeast part of Hangjinqi. Boerjianghaizi fault separated the research area into two parts, in which the south and north part have many differences. The north structures lie on Hangjinqi fault block of north Yimeng uplift, where nose bulges and several small structure bulges with southwestward plunge are developed. The south part in located in north Yishan slop, which is a southwestward monocline. The study area has low porosity and permeability reservoirs with low exploration degree.Based on the previous studies, well logging, sedimentology, petroleum geology and many other disciplines and research methods, the data of mud logging, well logging, physical property analysis test are collected and the study of lithology, physical property, types of pore, structure of pore and four characters relationship of reservoir is conducted, and then log interpretation model is established and the lower limit of reservoir and the evaluation standard of reservoir classification are fixed. The reservoir classification evaluation is established by the reservoir interpretation of single wells.The main lithology in study area are debris quartz sandstone, feldspar debris sandstone and lithic sandstone, which have medium sort grade, low psephicity and porous cementation dominated. The main types of pores are residual primary intergranular pores, secondary intergranular pores, intragranular dissolved pores and fractures, and secondary pores are the most common type. The reservoirs with low porosity and permeability have complex pore structure, and residual primary intergranular pores are only found in He2 layer. The porosity and permeability have obvious positive correlation, while displacement pressure and the median saturation pressure relatively have negative correlation with porosity and permeability, and max throat radius, the median throat radius and max mercury saturation relatively have positive correlation with porosity and permeability.The study on four characters relationship of reservoirs shows that the content of quartz has slight positive correlation with porosity, while the content of rock debris has negative correlation with porosity. With the decreasing of granularity, porosity and permeability decline accordingly. The porosity and permeability have positive correlation with sonic differential time and compensated neutron logging, while they have negative correlation with compensated density. Thus, the corresponding well logging interpretation model is established by lithology, physical property and electric property characters, which includes shale content interpretation model and physical property interpretation model.Combined with the above research, the lower limit standard of targeted reservoirs is set up which has a minimum porosity of 5% and permeability of 0.1mD. The porosity plan figures show that reservoirs with good physical property lie on the south part except He2-1 reservoir which is symmetrical distributed from the center to east-west direction. The reservoir sand distribution is dominated by braided channel sand bodies which are stripe-shape distributed. According to logging interpretation figures of single wells, the reservoirs are divided into three types: ?type reservoir with porosity larger than 13% and permeability larger than 1mD; ? type reservoir with porosity between 9%~13% and permeability between 0.5~1mD and ? type reservoir with porosity between 5%~9% and permeability between 0.1~0.5mD. In the light of overlay maps of reservoir distribution and porosity distribution, the favorable areas of reservoir are divided into two types: the most favorable areas have average porosity larger than 11% with thickness of sand larger than 12 m, and secondary favorable areas have porosity between 9%~11% with thickness of sand between 8~12m.