Analysis Of Diagenetic Evolution And Hydrocarbon Filling Issues Of Huagang Formation Tight Sandstone Reservoir In Xihu Sag

Gas exploration of Huagang formation in Xihu sag has acheived significant breakthrough recently,which is rich of resource.But the diagenetic evolution and hydrocarbon filling of tight sandstone reservoir experienced remains to be explored.Based on observation of the cores and and description of the rock thin sections,after reading quite a few references of home and abroad,combined with background of structure and sedimentary,we analysis the characteristics of petrologic,pore structure,physical property,diagenism,process of hydrocarbon filling of Huagang formation tight sandstone reservoir of D1,2 structure in Xihu sag with test and analysis data of well sample.We build the evolutionary sequence of diagenetic stage and summarize the process of diagenetic environment and hydrocarbon filling,also we achieved a series of achievements and recognizes.?1?After analysising a few of data of thin section description,grain size analysis and physical property of actual measurement,we ascertain the characteristics of petrologic,which is“one coarse,one high and three low”that is“the framework is coarse grained,the content of quartz is high,the content of muddy is low,the content of kaolinite is low,the content of cement is low”.The main distribution of the reservoir porosity ranged from 6%to 15%,which belongs to low porosity-super low porosity reservoir.The main distribution of the reservoir permeability ranged from 0.1 to 10×10^-3?m²,which belongs to low permeability-super low permeability reservoir.The rate of secondary pore contribution to the pore abundance of reservoir reached 72.15%,which is mainly content of dissolution porosity.?2?With the methods of SEM,cathode luminescence and description of the rock thin sections,we recognize the Huagang formation has experiensed three kinds of diagenisms like compaction,cementation and dissolution.The diagenism of compaction are throughout the whole process of sedimentary and diagenetic evolution.Calcite cementation is the main kind of cathode luminescence diagenism.The degrees of Kaolinite cementation,kiesel cementation and chlorite cementation have significant differences in different structures or different members.Multiphasic dissolution is the most important lithogenic factor.After analysing the test data of secondary silica and C,O isotopic element of calcite cement,we conclude that the acidic fluid is mainly contented of organic acid and part of it came form atmospheric eluvial water.Also,we recognize the diagenetic environment that Huagang formation experiensed.At the same time,we find out that the reservoir of northern D1 structure is in the A to B period of middle diagenetic stage,which is in the weak alkaline diagenetic environment.The reservoir of southern D2 structure is in the A period of middle diagenetic stage,which is in the acid diagenetic environment.?3?With the advanced test analysis methods and outcome of diagenetic evolution,burial history,thermal evolution and hydrocarbon filling evolution,we obtain the message that northern D1 structure has at least exercised three issues of hydrocarbon filling.The corresponded time distanced today is 19 to 17Ma?17 to9Ma and 7 to 0Ma.The second issue acid fluid occurred before the uplifting and has kept for a long time,which filled some hydrocarbon quantity and reconstructed the reservoir strongly.The third issue acid fluid occurred after settling and filled the largest hydrocarbon quantity,but it was balanced out by the alkaline fluid left before,which has little impact on reconstructing the nearly compacted reservoir.