Research On The Interlayer Of The Carboniferous Donghe Sandstone In Hudson Oilfield

Donghe Sandstone reservoir in Hudson Oilfield has entered the middle and late stages of development.The overall performance is characterized by high water content and rapid decline in production.The distribution of remaining oil is complex and the internal heterogeneity of the reservoir is serious.The existence of interlayer in reservoir is an important factor affecting its heterogeneity.The seepage difference caused by interlayer has a great influence on reservoir development.Through interlayer research,the problems in actual production can be solved as much as possible.In this study,comprehensive utilization of geological,logging,production and other data,the sedimentary characteristics of the Carboniferous Donghe Sandstone section in the southwest of Hudson Oilfield,the identification standard of interlayer,the causes of interlayer,the distribution of interlayer and the influence of interlayer on remaining oil are systematically studied.The main achievements and understandings are as follows :The Carboniferous Donghe Sandstone section of Hudson Oilfield is a wave-controlled coastal sedimentary body,which has experienced two stages of relatively rising and falling sea level.The lower section of Donghe Sandstone develops 8 to 6 layers,and the upper section develops 5 to 1 layers.From south to north,the thickness of Donghe Sandstone section gradually decreases until it pinches out.In the study area,there are coastal subfacies,foreshore subfacies,backshore subfacies and coastal sand dune subfacies.The characteristics and scales of three microfacies in each subfacies are different.The study area mainly develops calcium argillaceous interlayer,development of calcareous interlayer in the upper section of Donghe Sandstone,and argillaceous interlayer is developed in the lower section of Donghe Sandstone.Based on the comprehensive analysis of core and logging data of coring wells,the rock-electricity relationship of interlayer and the semi-quantitative identification standard of interlayer are established,and the Fisher discriminant method is used to identify and classify different types of interlayer more accurately.Through the regression of experimental data,the verification results are 89.8 %,among which the calcium argillaceous interlayer and calcium interlayer are better.The causes of interlayer in the study area are mainly argillaceous interlayer formed by sedimentation,calcareous interlayer formed by diagenesis,and calcareous argillaceous interlayer formed under comprehensive action.By studying the distribution characteristics of the interlayer and the spatial distribution model of 5 and 6 layers,it is considered that interlayer are most developed in the coastal subfacies environment,the argillaceous interlayer in the lower section of Donghe Sandstone is more developed than that in the upper section of Donghe Sandstone,and the calcareous interlayer in the upper section of Donghe Sandstone is more developed.And the interlayer of 5and 6 layers are the most stable.The interlayer are relatively developed in the southwestern,central and southern and northeastern part of the study area;Secondly,the stability of interlayer distribution has a significant control effect on the distribution of remaining oil.The control effect of interlayer on remaining oil in HD4-94 H well area,HD4-H92 well area and HD1-27 H well area is relatively good,and the enrichment of remaining oil is high.The interlayer with horizontal occurrence is more conducive to the enrichment of remaining oil than that with oblique occurrence.