The Application Of Statistical Methods In Petroleum Resource Assessment On Weixinan Depression, Beibu Gulf Basin

In recent years, China’s offshore oil and gas exploration has developing rapidly,and exploration investment increasing year after year, and achieved better explorationresults from2004to2010, the Beibu Gulf Basin Weixinan Depression had16oil andgas structures with new discovere, increased oil proved reserves8799.97×10~4t. By theend of2010, the proved oil reserves of Weixinan Depression was more than twohundred million tons, the proved degree get to63%, it indicated that the region hadentered to the Middle-Late term of exploration. in recent years, this depression shouldnot has such a big exploration breakthrough and the proved degree didn’t comply withthe current exploration and development situation, it was difficult to carry out the nextstep in exploration deployment, so it is necessary to further study and evaluation the oiland gas resources of Weixinan Depression.According understanding the degree of exploration of the study area, we applystatistical methods in petroleum resource assessment to evaluate the study area, usingthe Geostatistical method, field size sequence method, Generalized Pareto distributionmethod to calculate the petroleum geology resource of the study area. Through theseanalysis, we summed up some important recognitions as follows：(1)Ggeostatistical method considers the geological risk of evaluation unit, the sizedistribution and numbers of the undiscovered reservoirs, the evaluation area is dividedinto three longitudinal evaluation units and three planar evaluation units, the evaluationresults of the method shows that the petroleum geology resource of the study area is50745×10~4t, Weizhou formation’s potential is the greatest in longitudinal evaluationunit, the central zone’s potential is the greatest in plane evaluation unit; oilfield scalesequence method considers the serial number and the size of distribution of discoveredoil fields, evaluation results of this method show that the petroleum geological resourceof the evaluation area is53820×10~4t, the oilfield size of undiscovered oilfields is smallor medium; generalized Pareto considers the found serial number and the sizedistribution of discovered reservoirs, evaluation results of this method show that thepetroleum geological resource of evaluation area is49019×10~4t; Uising Delphi methodto weight these three methods, the evaluation results show that the petroleumgeological resource of the evaluation area is51150×10~4t. (2)Using Logistic model and Gompertz model to predict the reserve gro wth trendof2011-2040years of the Beibu Gulf Basin Weixinan Depression. Two modelpredictions indicate that the Weixinan Depression is in exploration peak period and itwill been had entered to the exploration of late term in2040; the exploration situationof2011-2020will remain good, proven reserve of years will be more than1000×10~4t;the predicted value of Logistic model is slightly larger than the predicted value ofGompertz model.(3)Should strengthen fracture combination study of the main oil layer of Weizhouformation and Liushagang formation in the future exploration, strengthen to analyseoil-Gas Pools forming rules of the unconformity between the Paleogene and the formerCenozoic, strengthen to explorate main hydrocarbon sag of subtle reservoirs and studythe lithologic reservoirs of southeast play.