A Study On Gas Reservoir Description Technology Of Upper Paleozoic Tight Sandstone In Ganquan Area,Ordos Basin

In order to solve the problems existing in natural gas development in Ganquan area of Ordos basin,such as unclear distribution rules of main gas reservoirs,low reserve abundance and single well production,frequent channel migration and swing,difficult deployment of development wells,and difficulty in guiding and tracking horizontal sections of horizontal wells,the description technology of tight sandstone gas reservoirs in the upper Paleozoic in Ganquan area of Ordos basin was studied to clarify the distribution rules of main gas reservoirs,Clarify the control factors of natural gas enrichment and provide strong geological support for the deployment of natural gas development wells in Ganquan area of Ordos Basin.This paper takes the 8^th member of Shihezi Formation,the 1^st member of the Shanxi Formation,the 2^nd member of the Shanxi Formation and the Carboniferous Benxi Formation in the Ganquan area of the Ordos Basin as the research target interval.Through the comprehensive analysis of the drilling data,coring data,logging data,gas testing data,conventional analysis and test data and special analysis and test data in the research area,the gas reservoir description technology of the target interval is studied.The research content includes five aspects,including stratigraphic characteristics,structural characteristics,sedimentary characteristics,reservoir characteristics,natural gas enrichment rules,and favorable area prediction.Through the research of this paper,the following achievements and understandings have been achieved:（1）There are significant differences in the thickness differentiation of the Benxi Formation;The thickness distribution of the Shanxi Formation～8^th member of Shihezi Formation is relatively stable;The top structural features of the Benxi Formation～8^th member of Shihezi Formation are all characterized by a gentle westward dipping monocline,with locally developed small nose shaped uplift structures and no developed fault structures.（2）The sedimentary system of the Benxi Formation is divided into barrier coasts,and the sedimentary microfacies are mainly composed of barrier sandbars and lagoons;Under the control of the reciprocating migration of the coastline,in the northern part of the study area,the continuity of the barrier sand dam in the Benxi Formation is good on the plane,extending in a“long strip”shape,and the sand body generally trends in a northeast or nearly east-west direction;In the southern part of the research area,the continuity of the barrier sand dam in the Benxi Formation is poor on the plane,and the plane shape is“potato shaped”,with an overall distribution in a northeast or nearly north-south direction.The sedimentary system of the Shanxi Formation～8^thmember of Shihezi Formation is divided into delta front,with sedimentary microfacies mainly consisting of underwater distributary channels and underwater interdistributional bays;The development of 8-9 underwater distributary channel belts in the Shanxi Formation～8^th member of Shihezi Formation runs through the research area in a nearly north-south direction.（3）The median permeability of the test samples from the Benxi Formation～8^th member of Shihezi Formation is less than 1.0m D,indicating a tight sandstone gas reservoir;The spatial distribution of gas reservoirs is controlled by sedimentary facies;The regional enrichment of gas reservoirs is controlled by the physical properties of the reservoir.（4）The Benxi Formation is a favorable target layer for gas reservoir development in the study area;The northern region is a favorable target area for gas reservoir development in the research area.