Lithologic And Stratigraphic Oil-gas Reservoir And Favorable Exploration Zone Predictions For Upper Zhujiang Formation In Huizhou Depression And Dongsha Massif Of Pearl River Mouth Basin

Huizhou depression is the main depression of the Pearl River Mouth Basin,whereas Dongsha Massif is the main convergence belt of the oil-gas migration of Huizhou depression and one of the important investigated areas at Pearl River Mouth Basin There are different traps in this area,such as structural trap,lithotogic trap,stratigraphic trap and structural stratigraphic trap.Having been explored for about 30 years,most apparent structural traps in this area were finished misering.To improve the industrial production of the oil-gas,conducting the investigation of the lithofogic and stratigraphic reservoir has been the inevitable trend of the exploration activity development recently.Referring to the theory of high-resolution sequence stratigraphy theory,recognized the sequences boundaries and flooding surface on each wells by major unconformity,sedimentary discontinuity,lithological sudden change and the conversion of parasequence stacking pattern At the same time,analyzed the reflection structure and its response characteristics on seismic,then built up the isochronous stratigraphic framework in studied area which divided the upper Zhujiang Formation into two third stage sequence and seven forth stage sequence.What' more,through the correlations between well and well also combined with the sequences tracking on seismic,the developed situation and distribution feature of every sequence has been studied.Sedimentary facies distribution and prediction are carried out under the sequence stratigraphic framework.Considered the characterization of sedimentary evolution,logging and the drilling cores,three kinds of sand bodies,which are beneficial to the formation of lithofogic and stratigraphic traps,are recognized.Based on the characterization of these sand bodies,four favorable areas of sedimentary facies are concluded.Lithologic and stratigraphic traps were controlled not only by sedimentary factors but also by structural factors.Influenced by the direction of provenance,only the structural wedge out protrudes toward west can it intersects with sedimentary wedge out so as to form the Lithologic and stratigraphic traps.In accordance with the possible structural characterization that can form lithologic and stratigraphic traps,we discerned four structural types,and we also discerned nine favorable areas beneficial to lithologic and stratigraphic traps.After analyzing the migration patterns of oil-gas and the distribution of important structural ridges,we come vsp with the method to divide the reservoir-forming system of depression-fault ramp-structural ridge-trap.The reservoir-forming system in this area was divided into four types including dip reversal anticline,massif,buried hill and palaeohigh.Based on the characterization of the reservoir-forming system,six favorable areas were preferably chosen out.Considering the factors of sedimentary evolution,tectonic evolution and reservoir-forming system universally,three favorable exploration areas were proposed.Then use the geophysical methods to evaluate the effectiveness of the reservoir in these favorable exploration areas,which provided a scientific basis for depth exploration and development.