Abstract

A great majority of the productive reservoirs in Daqing Oilfield are composed of various kinds of fluvial channel sandstones. Under the condition of no outcrop, lack of analogous modern deposits available for detailed investigation, basing on the rich experiences of our research on reservoir sedimentary facies, as well modern fluvial sedimentological knowledge, a new research method is developed, that is, taking advantages of logging curves of close well pattern on a large area, and to gradually analyze sandbody geometries and their internal architectures, and to finely construct sedimentation models of fluvial facies reservoirs, and to describe reservoir heterogeneity finally. By applying this to subsurface reservoirs in large scale, four types of sedimentation models of fluvial channel sandbodies in PI1–3 zones are systemically constructed. Infill drilling and production test data have proved the credible accuracy and wide adaptability of the models.

Introduction

The main productive reservoirs in Daqing Oilfield are a suite of large fluvial-delta deposits in the Songliao lake basin. Many kinds of fluvial channel sandstone reservoirs cover a fairly important proportion of reserves. They are developed in a great variety complicated geometries, different scales, and internal irregularities. Cutting and superimposing one another, and coexisting closely with sheet sands, the sandstones form intricate heterogeneous reservoirs. After a long period of waterflooding, most of the channel sandstones have entered a late stage of high water cut, but there is still considerable residual oil with complex distribution, so it is hard to find out and develop. To tap the potential of this part of reservoirs, a continuous production adjustment is carried out and many kinds of EOR projects are conducted. All of these need cooperation of detailed reservoir description in order that a good outcome can be obtained.

According to the special geological characteristics of Daqing Oilfeld, to construct detailed sedimentation models of reservoirs, which tallies with actual situation, are bases and keys to detailed description. This work is usually conducted first in outcrops or analogous modern deposits. Unfortunately, Daqing Oilfield has no its owner analogous outcrops, and lacks detailed investigation data of modern deposits either. What we can do is only to start with subsurface data. For thin interbedded alternating reservoirs, present seismic data can do nothing with them. Under this circumstance, relying on our research experiences in the study of reservoir sedimentary facies, and fluvial sedimentological knowledge, after repeated practices, a new method to construct detailed sedimentation models of fluvial facies reservoirs is found out after using close spacing logging curves on a large area. By applying these research thoughts to substance in large scale, four sedimentation models of fluvial channel sandbodies are constructed.

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