Reservoir Characteristics And Logging Evaluation Of The Ma 5 Member Of The Majiagou Formation In Area A Of The Sulige Gas Field

Sulige gas field,located in the northern Ordos Basin,is one of the largest gas field of our country.Majiagou Formation of Lower Paleozoic reservoir in this area is a typical set of carbonate reservoir.Concerning on A Block in Sulige gas field,this paper mainly studies on reservoir characteristics of the major gas producing strata of Majiagou Formation and well logging evaluation intended to provide the basis for reservoir evaluation of study areas.On the basis of the comprehensive utilization of core data,logging data and geological data,this paper firstly studies on reservoir characteristics of the major gas producing strata of Majiagou Formation in terms of petrological characteristics,physical characteristics,lithologic character and types of reservoir space.And found that the reservoir rocks of Majiagou Formation are dominated by dolomite.Reservoir space mainly develops die,intergranular pore,intergranular dissolved pore and fracture,and so on.Overall reservoir physical property is poor with the characteristics of low porosity and low permeability.Secondly,based on the cores and thin sections and well logging data,the sedimentary facies and sedimentary microfacies are analyzed,showing that Majiagou reservoir development bedding,bird's eye structure,tuberculosis and other sedimentary structure,belongs to tidal flat subfacies;the main types of sedimentary microfacies are dolomitic flat,limestone-dolomitic tidal flat and muddy dolomitic flat.Thirdly,this paper builds up logging interpretation models of shale content,porosity,permeability and gas saturation,which are suitable for carbonate reservoir of study areas base on core data,logging data,and validate the various models,which have high accuracy and good applicability.By using the combination of empirical statistics and cross plot method,this paper confirms the lower limit of physical property of reservoir.The lower limit of porosity is 1.6%,and the lower limit of permeability is 0.024 ×10-3 ?m2.Fourthly,this paper uses crossplot method and lateral-array induction method to identifying reservoir fluid property.These two methods can all distinguish between the gas,water and gas-water layer,and the crossplot method has the best recognition effect.In practice,various methods can be used to identify the fluid properties in order to gain better results.At last,based on the analysis of the control factors of reservoir distribution,in the light of sedimentary microfacies types,porosity,effective thickness and acoustic travel time,this paper adopts the way of assignment to make favorable areas selection for the major gas producing strata of Majiagou Formation in study areas,drawing a conclusion that there are three favorable areas classed ?,twelve favorable areas classed ?,twelve favorable areas classed ?.Among them,the ? types of favorable areas have the highest value of exploration and development.