Study Of The Hydrocarbon Accumulation Rules And Fine Exploration Of Hydrocarbon Reservoirs Of South Sumatra Basin,Indonesia

Guided by sedimentology,sequence stratigraphy and mathematical geology,this study is foucus on the reservoirdevelopment and distribution which controlled by the stratigraphic sequence framework and base-level cycles,to provid more useful information for the hydrocarbon accumulation study and fine exploration.With a lot of drilling data,logging data,seismic data and outcrop sections as the first-hand resource,a accurate geological model has been established basing on the sedimentary system and base-level cycles,phased sedimentology and mathematical modeling to make full use of various geological variables specially reservoir geological variables which have close relationship with the sand distrbution.Based on geological models,research reservoir development and distribution by the base-level cycle sequence making a clearer understanding of the reservoirand its distribution.That's greatly improving reservoir prediction accuracyand to be the guideofhydrocarbon accumulation.This is good for the old petroliferous districts andimprove therolling exploration.This paper is the inheritance and development of traditional sequence stratigraphy.Further study the technical essence,practicability and limitations of Vail,Galloway,Johnson and Cross theorys.It is believed that the first three theorys which emphasis on sea-level change controlling the tratigraphic formation and phase distribution are not proper to continental strata.Cross theory stress the base-level cycles theory,and it applies to both land and marine strata.Recently petroleum exploration practice prove that it more suitable for some continental system which are not affected by the Sea(Lake)level rise and fall,such as alluvial fans,river Delta,submarine fans so on.Therefore,accurate geological model established by the guidance of the traditional sequence stratigraphy theory,phased sedimentology,the model of sedimentary facies belt,cross theory,mathematics geology modeling method.The modle has more accuracy in reservoir prediction.Three sequence stratigraphic framework have been divided by tectonic and sedimentary evolution in south Sumatra basin by the base-level cycle theory.Analyzing the different sedimentary systems,sedimentary facies to predict the favorable reservoirs.The source-reservoir-cap rock assemblage should be made clear to carry out the hydrocarbon accumulation rule reserch which is most important in the rolling exploration and development.The project of this paper is a keyproject of Petrochina company.Analying the reservoir-forming rule and evaluation the exploration targets of south Sumatra basin of Indonesia.(No:Y2013JF8-02).The method is to integrate study the relationship of geology,seismic,sedimentary,petroleum accumulation system.South Sumatra basin can be divided into three sequence stratigraphic framework by tectonic and sedimentary evolution.Different sedimentary facies of the sequence the source-reservoir-cap rock assemblage should be made clear to predict the favorable reservoirs.This paper has 10 special topics around the core:Regional tectonic characteristics andevolution;Drilling delamination and seismic sequence frame establishment;Sequence system tractscharacteristicsand sedimentary filling evolution;sequence interface characteristicsof the key hydrocarbon bearing series;Seismic & Sedimentary facies and their distribution;seismic attribute analysis,reservoir inversion,prediction & evaluation;source reservoir cap assemblage analysis and prediction;Seismic frequency response and hydrocarbon detection;integrated study the hydrocarbon accumulation rule by structure,sedimentary,reservoir,and hydrocarbon detection;favorable areas of hydrocarbon accumulation identification and targets of rolling exploration evaluation.There are three innovations achievements as fellows:1.Based on the regional tectonic background and the evolution characteristics of the basin,the target layer accurate geological model study is to be carried on.On one hand,single well and multiple wells sequence division have been done to divide the study area sequence.On the other hand,deterministic modelingand stochastic modeling analysis is combined to set up the study area reservoir facies-controlled model.On the basis of the study on the sedimentary facies belt distribution characteristics of the target layer,the reservoir in the sequence boundary is predicted accurately,thus solving the bottleneck problem of long term reservoir understanding in the study area.2.Summed upa set of reservoir predictionmethodsunder the control of "facies controlled sequence stratigraphy",and oil and gas accumulation rules.Based on the function of definition of sequence phase controlled sequence model and wellbore data and seismic attributes in the cognition of reservoir prediction,combined with the comprehensive analysis of drilling,build up a more quantitative model of reservoir prediction and reservoir descriptionfor oil and gas exploration target layer.As a result,a lot of stratigraphic and lithologic reservoirs exist in the middle and eastern part and large structural reservoirs in the west.This make the hydrocarbon rolling exploration more precision,and are good to the future establishment and application of hydrocarbon exploration model.3.Through combination of stratigraphy,sedimentology and reservoir sequence,a reservoir model of sequence control deposition and eservoir deposition determine the decision of oil and gas reservoiris built.The exploration and working method of stratigraphic lithologic oil and gas reservoirs are putting forward,and the problem of some technical bottlenecks in exploration is solved in the practical work.Technical bottlenecks have been solved with the improvement of hydrocarbon exploration idea and the working method,which play a positive role in Indonesia exploration and make it easy to know the hydrocarbon accumulation rule to get the good exploration effects.For example,the production increased from 2 million tons to 6 million tons and remained at around 5 million tons in recent years.