The Research Of Reservoir Prediction Of The Second Member Of Xujiahe Formation In HBC Area

The studying area is located in the center-south transition zone of median foldhigh and steep structure area and the mesoid fold gentle structure area, southeast ofSichuan Basin.This area has the features of stable regional structure, undevelopedfracture and weak interacting of regional tectonics on sedimentary cover. Its strikedirection presents declinate monoclinal folding, ventral structure develops integratedand gentle.The area also doesn’t have large scale anticlinal trap. Its east area is obliqueeastern median fold high and steep fold belt. It’s adjacent to Jieshichang structure inthe west southern area, Luoguanshan structure in the southern area, Dazu-Anyuesyncline in the northern area and Xishan structure in the eastern area. Xujiahe groupmainly develops abnormal fault, it presents gentle slope in the northeast area. Whilein the southeast area, because of Southeast Sichuan median fold high and steepstructure, faults develop. Ventral faults distribute in the limb of nosing fold, majorityof tilting axisthrust fault. Overall, performance of the faults is little fault displacement,few horizon and shortness plane extension in the vertical (Fig1). In the studying area,Xujiahe group deposits Delta-Lacustrine sedimentary environment. The reservoirmainly consists of mouth bar sand body and distributary channel. The formation is aset of sand and mudstone alternate layer. Rock types are fine-medium grain quartziticarkose, medium-macro grain quartzitic sandstone and little lithic quartzitic sandstone.The research object is the second member of Xujiahe Formation. The core is theresearch of reservoir forecast. The achievements are:1. Through the analysis of single well facies and reservoir comparison of welltie,recognizing that in the HBC area, reservoir develops in the upper part of secondmember with good porosity and interconnectedness, individual reservoir is thickness,could form wild porosity reservoir.2. Combining seismic, geology and logging as the core idea, using the interaction of geology and geophysics, such as reservoir replacement and composite recording toresearch formation of reservoir seismic reflection.Finally, establishing two kinds ofbeneficial reservoir seismic response pattern of the second member of XujiaheFormation. One kind is low frequency、high amplitude、event push-down; the otherkind is the position that located in the inside of the second member of XujiaheFormation with high frequency、parellel-subparellel reflection and high amplitude.3. Through the comparison of inverse section and actual drilling, considering thatthe method of modeling annealing inverse applies well in the studying area, itcompletes gamma inverse of the whole area, velocity inversion and porosity inversion,analyzing distribution features of reservoir on section. It can be used as the referenceof selecting well location.4. Fracture forecast using coherent detection、discontinuous detection、stress fieldmodeling detection、micro-fault image-forming and pre-stack nonisotropy faultdetection of post-stack seismic data. Every kind of detection can obtain similar results,but existing some differences. Post-stack detection is sensibility to macro fault system,while it can be influences by various effects.5. Fluid examination using the high frequency decay technical and low frequencyaddition technique that based on minor undulation transform, through the filtering ofmudstone, removing the influence of mud. Ultimately, obtaining the fluid’sdeveloping characteristics of the second member of Xujiahe Formation.6. Establishing the pattern of gas producing well which can be used as thefoundation of next exploration. There are four conditions that good to form oil andgas accumulation: the combination of the micro fracture that near fault and highporosity reservoir; high accumulation factor; developmental micro fracture andhydrocarbon enrichment zone.