Evaluation Of Hydrocarbon Source Rock By Logging Method

The accurate geochemical indicators of hydrocarbon source rock can be obtained from the core samples.While influenced by the number of samples and the limited testing cost,continuous analysis data is difficult to get.Research shows that logging data can indirectly obtain the information of lithology and fluid.The vertical resolution of logging data is high and accurate,which can make up for the deficiency of hydrocarbon source rock evaluation by chemical analysis data.On the basis of the standardization of well logging curves of Fenchuan area,Nanniwan oilfield,this paper,first of all,identities the hydrocarbon source rock of Chang 73 by overlapping GR curve and AC curve,statistics the hydrocarbon source rock's thickness of each well,draws out the thickness distribution plane of hydrocarbon source rock,and analyzes its distribution characteristic;Then,the research analyzes the deficiencies of the traditional ?logR method and uses multiple regression statistical method on the calculations of organic matter abundance of hydrocarbon source rock,fitting the regression model and applying to the whole study area to calculate TOC of every well and to evaluate organic matter abundance of hydrocarbon source rock;Finally,based on the thickness and TOC,this paper classifies the hydrocarbon source rock to four categories.The results show that contents of organic carbon content and chloroform bitumen "A" are high,and the hydrocarbon potential and hydrogen index are medium;organic kerogen is type II,which means the organic matter is mainly from terrestrial plants;Ro is generally between 0.5% to 1.3%,and Tmax is mainly between 443? to 451?,with an average of 447?,which means the hydrocarbon source rock in the bottom has been mature and Tmax is just in the source peak;total organic carbon ranges from 2.3% to 4.6%,with an average of 3.6%;The oil shale is mainly developed at the bottom of Chang 7 member,and it is thinner in the northeast than it is in the southwest.The thickness of hydrocarbon source rock ranges from 10 m to 22 m,with an average of 16 m,with the good continuity and stable distribution.For first category,thickness is greater than 15 m and TOC content is more than 3.6%;for second category,thickness is greater than 15 m and TOC content is less than 3.6%;for third category,thickness is less than 15 m and TOC content is more than 3.6%;for forth category,thickness is less than 15 m and TOC content is less than 3.6%.The area of first category is the biggest,which takes 45% of the whole study area.