Comprehensive Evaluation Of Mudstone Caprocks In The Middle Of The First Member Of Shahejie Fm In The Qikou Sag

Mudstone seal in the middle of the first member of Shahejie Formation in Qikou Sagwas comprehensively evaluated by using well logging data, drilling data, test data. Throughcounting more than200Wells in the thickness of the accumulated mudstone in the middle ofthe first member of Shahejie Fm in the Qikou Sag, we paint cover thickness plane distribution.The results show that the caprock was generally thick mudstone accumulated large thickness,mudstone accumulative total thickness on the southeast to northwest gradually increases thicktrend; This set of the cover of the thickness of the high value total area mainly distribute in thenortheast of the depression, and it appears as two north east-south west to parallel arrays withtwo high value, which are more than500m high. Using the function relationship betweendisplacement pressure and depth and shale content product, we study the seal of displacementpressure plane development characteristics. The displacement pressure in middle of the firstmember of Shahejie Formation in Qikou Sag appears main present for presenting therise-reduce-rise-reduce-rising trend of fluctuations from south to north. High value areas arelocated mainly in the northern Banqiao depression, the northeast, the western and easternNandagang buried hill structure belt. Based on the study of Macro development andmicroscopic characteristics of the regional seal in the middle of the first member of ShahejieFormation in Qikou Sag, at the same time, we take account of fault displacement pressurealso as an important parameter. Choosing the three parameters depth of cover, that isdisplacement pressure and gas reservoir pressure coefficient. Firstly the parameters isnormalized and then we can make a comprehensive evaluation to caprock sealing ability ofShahejie Formation in Qikou Sag. The results show that the high value of comprehensiveevaluation sealing capacity on the whole area along the qikou sag distribution, graduallyreduce on both east and west sides. The high value of comprehensive evaluation, also exist inlocal areas of Banqiao sag. The most areas in regional seal in the middle of the first memberof Shahejie Formation in Qikou Sag have closed, low abundance of gas reserves ability, andthe sag area have closed high abundance of gas reserves ability. The gas reservoir evaluationresults compared to gas reservoir characteristics at present is accordant, so the correctness ofthis method is proved. From the comprehensive evaluation level, we can see that the seal ofmiddle and above comprehensive evaluation level is beneficial to hydrocarbon accumulation.From the time match relation between caprock and source rock, we can see that the coversealing ability of Shahejie Formation in Qikou Sag is mainly formed in the later period Dongying group; at this time for source rocks in the middle of the third member of ShahejieFormation is not yet at a row of oil and gas, so the cover of time for oil and gas in the closedeffective, which is helpful to cap oil and gas, and helpful to oil and gas accumulation. In thespace, the cover development in thickness in the middle of the first member of ShahejieFormation in Qikou Sag, and in the study area it is distributed. At the same time the distancebetween the cover and source rock in the middle of the third member of Shahejie Formation iscloser, so in space it is effective to oil and gas accumulation. Finally through the research thecover of close condition with different reserves abundance reservoirs, we can establishdifferent reserves abundance of cover thickness, displacement pressure sealing capacity andcomprehensive evaluation parameters of the corresponding standard, thus, we can predictadvantageous areas which are closed by the first member of Shahejie Formation.