Research On Thick Oil Layer Reservoir Architecture

After years of enhanced exploitation, most of old oilfields in East China have entered high-cut stage right now. The water cut could reach into95%, but oil recovery is comparatively low that about30%-40%. The research shows remaining oil which is affected by a variety of geological and development factors can be found in thick oil layer underground with different scale and distributes. The complex internal structure of thick oil layer is an important factor causing the reservoir heterogeneity, and it controls the flow of underground fluid. Therefore, the research on reservoir architecture of thick oil layer and effect of reservoir architecture on remaining oil at this stage, has important significance for guiding potential tapping remaining oil in the old oilfields.Eastern Wen25Block is located in Puyang County of Henan province, in the northern part of central uplift Dongpu Depression, bordering thePucheng Oilfield to the north, Liuzhuang tectonic belt to the south, Liutun sag to the west, Liyuan sag to the east, that is a complex northeast-trending fault block oil and gas field inclusion of graben and horst.In this paper, taking the lower part of the second Shahejie sub-member in Eastern Wen25Block as a case, aimed at reservoir geological and development characteristics of Wenliu Oilfied, with the guidance of sedimentology, petroleum geology, sequence stratigraphy and reservoir structure factor analysis, under the comprehensive analysis of core data, logging data, seismic data, dynamic data, using the method of scale analysis and model fitting, the architecture of the thick oil layer is precisely anatomized, each grade of architectural element distribution is quantitatively described, a three-dimensional geological model of reservoir is established, the remaining oil distribution patterns controlled by reservoir architecture are analysised, a suitable reservoir architecture analysis method of underwater distributary channel based shallow delta is proposed, which will help to study the characteristics of the simillar reservoir in the other oil fields, as well as guiding potential tapping remaining oil and improving oil recovery.Based on core data and logging data, from the viewpoint of sedimentology, and using the sedimentary cycle method, equal thickness and height rule, the formation of study area is divided into8layers,42depositional unit, an accurate sequence frame of the scope of the entire area is eventually established.On the basis of accurate sequence frame of the scope, the study on distribution of sedimentary facies within stratigraphic framework is carried out. Based on the comprehensive analysis of a variety of laboratory data with coring data, through the analysis of the sedimentary characteristics, depositional environment, the researcher holds that the facies of study area are mainly underwater distributary channel based shallow water delta front facies, which are divided into4microfacies, namely underwater distributary channel, overbank, sheet sand, lake mud. The sedimentary model of the lower part of the second Shahejie sub-member in study area is established on the basis of the previous work.Based on core data and well logging data, aimed at microfacies as subdivision object, using analytic hierarchy method, various depositional interfaces within different microfacies are identified and classified, the grading scheme of the interfaces of reservoir architecture and architecture elements is identified, and3-5th grade architectural elements are the focus of this study, then carry out research on reservoir architecture between non-coring wells by the establishment of various rock electrical response models of architecture elements; Study on architectural elements combination models in plane and profile with the constraint of depositional model and dynamic data, focusing on the fourth grade architectural elements combination models. Based on this,7kinds of the fourth grade architectural elements combination models are summed up including lateral splicing type with different elevations, lateral splicing type with same elevation, lateral separation type, ectopic migration type, lateral migration type, vertical superposition type, and vertical separation type; By extracting modeling parameters of architecture elements and using hierarchical modeling method, using a combination of qualitative and quantitative approaches, a three-dimensional model based on reservoir architecture elements is established.Using the results of reservoir architecture research, especially the architectural elements combination models, combine with analysis on architecture elements and the permeability differences on its interfaces and reservoir performance, the formation mechanism of remaining oil under the control of reservoir architecture is analyzed, the distribution of remaining oil is forecasted. The research findings are instrumental in production practices in oilfields.