The Reservoir Conditions And The Forming Mode Of Assa Gas Field In Marsel Area,Southern Kazakhstan

The Assa block,located in Marsel exploration area at the north and middle of Kazakhstan,is an important exploration area in Marsel exploration area.It reveals favorable prospect of gas,but the conditions of petroleum accumulation and distribution are not yet very clear.Large numbers of internal and external literature were consulted and a vast amount of data collected while writing the paper.The paper is intended to determine the types of gas reservoir,analyze the accumulation mechanism,and establish the gas accumulation patterns on the basis of previous studies though source rock evaluation,reservoir evaluation,and the accumulation mechanism research,and the follow understanding has been reached:(1)The main source rocks are limestone,grey mudstone and shale,with a high organic material abundance and the type-II2 matrix as the main organic matter type,which is in the stage of high maturity,and the door limit of gas threshold between 1500m-1700m;(2)The gas reservoir types in the study area are mainly tight gas reservoirs;The carboniferous reservoirs are mainly limestone and marl,which belongs to dense limestone gas.The upper Paleozoic reservoir are mainly sandstone and conglomerate,which belongs to tight sandstone gas with pore structure,porosity and low permeability;(3)The power of natural gas migration is mainly gas expansion force,and the oil and gas conduction system is mainly fracture;(4)The contribution of gas is controlled by structure,formation,source rock,reservoir,favorable facies belt,etc.