Study On Micro-Pore-Throat Characteristics And Gas Flow Of Dense Glutenite Gas Layer In X Fault Depression

Many drilling wells in Shahezi Formation reservoir of X fault depression have encountered dense gas flow,and one of them produces a large amount of gas flow,which is close to the need of industrial production.It is of great significance for large-scale production of dense gas in this area.The pore throat characteristics of reservoirs in this area are relatively weak,and the flow characteristics and flow laws of fluids are not well understood,which makes it difficult for further exploration and development of gas fields.Therefore,it is urgent to analyze and study the pore throat structure and gas flow characteristics in detail to provide reasonable theoretical guidance for gas field development.Based on the experimental data of scanning electron microscopy,casting thin section,high pressure mercury injection,nuclear magnetic resonance(NMR),CT experiment and nitrogen adsorption,under the guidance of NMR theoiy,capillary mechanics theory and seepage theory,this paper studies the micro-pore throat structure,fluid characteristics and fluid flow law of the compact glutenite reservoir in this area.The fallowing understandings were obtained:Based on various experimental data and under the guidance of geological theory,it is determined that the reservoir of Shahezi Forlation in X-fault depression belongs to tight glutenite reservoir.Under the guidance of throat theory,Shahezi Formation is classified as micro-porous and micro-throat reservoir.The throat radius is generally less than 0.6 um,and a large number of dissolution pore are also developed.The combination of intergranular pore and dissolution pore is well developed in this area,and the combination of intergranular pore and micro-crack is slightly less,which mainly controls the throat position.According to NMR and high pressure mercury,gas-water infiltration experinent and wettability experiment,the distribution of pore and throat and clay content are the key factors determining the gas-water phase permeability characteristics,and the throat radius and the connectivity between throats control the bundle.Irreducible water saturation.Through the study of clay minerals in this area,it is found that there are more kaolinite,and these kaolinite will fill the reservoir space greatly.In addition to kaolinite,illite and chlorite with relatively low content were found,which resulted in the increase of bound water content,hindered the flow of movable fluid and restricted the developlent of tight gas reservoirs in this area.In the Shahezi Formation reservoir,the rock has strong hydrophilicity,so the bound water content is high,and the flow ability of gas phase is controlled by clay content and throat radius.The lower limit of porosity and permeability is 3.12%and 0.062 MD respectively by calculating the thickness of bound water film and establishing relevant models.