Heterogeneity Characteristics And AVO Responses In Tight Reservoir

Tight gas is one of the most important areas of unconventional natural gas exploration in the world.China has abundant tight gas resources.In recent years,the exploration and development of tight gas has continuously made new breakthroughs and demonstrated prospects.The tight reservoir has the characteristics of large buried depth,strong diagenesis,poor physical properties,complex oil/gas-water relationship and strong heterogeneity.Due to the tight reservoir conditions,tight reservoir with strong heterogeneity often has high-porosity zones or fracture zones,which are indicative of the exploration and development of commercial capacity oil and gas.Therefore,the characteristics of reservoir heterogeneity analysis are carried out.It is of great significance to find sweet spot of oil and gas reservoirs in tight oil reservoirs with tight and low abundance.At present,seismic data is rarely used in reservoir heterogeneity research,which results in limited macroscopic characteristics of reservoir heterogeneity.The strong heterogeneity of tight reservoir makes conventional seismic reflections have no specific response,using conventional geophysical methods cannot effectively predict reservoir distribution and gas-water distribution relationships.AVO technology refers to the technique of studying the basic properties of reservoir and the distribution characteristics of oil and gas by studying the variation of seismic reflection wave amplitude with offset.At present,the research on AVO technology has become more and more mature,and the AVO theory including rock physical properties is becoming more and more perfect.The characteristic parameters of reservoir lithology,physical properties,pore fluid and fractures distribution can be better obtained by AVO technology.The uneven distribution of these characteristic parameters is just the focus of reservoir heterogeneity research.Therefore,it is of great significance to apply AVO technology to the study of heterogeneity in tight reservoirs.In this paper,in view of the actual needs of tight gas reservoir exploration,a large number of research literatures are conducted to study the heterogeneity characteristics and influencing factors of tight reservoirs,and the tight dolomite reservoir of the fourth member of the Sinian lamp in the MX22-GS1.The characteristics of reservoir heterogeneity are analyzed.Based on the successful experience of AVO technology in other blocks,the reservoir thickness and caprock thickness of the tight dolomite reservoir of the fourth member of the Sinian lamp in the MX22-GS1 are analyzed.Porosity and AVO response characteristics of siliceous interlayers,and obtain the corresponding AVO response.The results of heterogeneity analysis of the tight carbonate reservoir of the fourth member of the Sinian lamp in the MX22-GS1 indicate that the micro-heterogeneity of the carbonate reservoirs in the target interval of the study area mainly includes lithologic heterogeneity.Sexual and pore structure heterogeneity.The lithology is mainly sand dolomite and various types of algal dolomite,as well as siliceous dolomite and vermiculite strips.Both the secondary pores and the primary pores of the target interval are developed.The macroscopic heterogeneity of the tight carbonate reservoirs of the fourth member of the Sinian lamp in the MX22-GS1 mainly includes: formation thickness,siliceous interlayers,porosity and permeability,and heterogeneity caused by the development of fractures and caves.The main influencing factors causing the heterogeneity of the tight carbonate reservoir of the fourth member of the Sinian lamp in the MX22-GS1 include tectonic,sedimentary and diagenesis.The structurally induced differential erosion is an important factor affecting the heterogeneity of the formation thickness and the development of fracture faults;the type of sedimentary facies determines the lithological heterogeneity and porosity heterogeneity of the target interval of the study area.Diagenesis plays a major role in controlling porosity heterogeneity,lithology heterogeneity,and formation heterogeneity caused by dissolution fractures and dissolution caves.Through the AVO forward modeling of single well variable parameters(caprock thickness,reservoir thickness,porosity and siliceous content)and the statistical analysis of AVO forward simulation of actual wells,the four sections of the GS-MX block light were induced.The AVO responses of the main parameters of homogeneity,combined with the P and G values obtained from the actual well AVO forward simulation,plots the three parameters of the P value,G value and caprock thickness(reservoir thickness,porosity,siliceous content).Figure,comparing the obtained law with the PG intersection graph of single well,can get the following AVO response law: AVO type shows the conversion pattern of ?—>?—>? with the increase of caprock thickness.With the thickness of the reservoir increasing the AVO response type to present the conversion pattern of ?->?->?.With the increase of reservoir porosity,the AVO response type shows the conversion pattern of ?->? or ?->?,and the reservoir increases with the increase of porosity.The AVO response types will eventually be converted to Class ? AVO;as the silicon increases,the AVO response type will exhibit ?->?.