Abstract

This paper introduces the performance history of the Daqing Oilfield and analyzes the potential for further development.

The residual oil distribution characteristics are analyzed taking the advantage of the core data of Well La8-JP182 and Well Bei1–330-J49. Then the numerical simulation method is used to analyze the recovery ratio, production rate, and the variation of pressure gradient under different production conditions. Finally, the technology of potential tapping of the isolated untabulated reservoirs, tabulated reservoirs, the huge thick reservoirs, and multiple rhythm reservoirs are brought forward in this paper.

Introduction

Daqing Oilfield has undergone the water flooding stage, the artificial lift production stage, and the stage of polymer flooding since the oilfield was put into production in 1960. The pressure gradient between the producers and the injectors were raised after each conversion of the stages. As a result, the pressure gradient rose from 0.15MPa/60m in the flowing production stage to 0.62MPa/60m in the polymer flooding stage. The production rate and the recovery ratio were increased. There is little room left for increasing the pressure gradient further. Whereas, The analysis of the reserve potential in Daqing placanticline area indicated that the residual recorerable reserves in basic well pattern and the first round infilled wells pattern are still relatively reacher, which is 19,287×104tons and 14,871×104tons respectively. Therefore, the optimization and the combination of various development regimes, the production methods should be taken into consideration to tap the potential further. Moreover, the efficiency of the combinations should be forcasted either through numerical smulation method. The following pages analyze the residual oil potential in Daqing Oilfield, the simulation results, and the technologies to be taken for different layers.

Residual Oil Potential Analysis

The Daqing Oilfield has been developed for 44 years. And 36.81% of the total OOIP has been produced by water drive method, which accounts for 75.57% of the recoverable reserves. Current water cut of the oilfield is 88.9%. The annual output of polymer flooding is 1,134×104tons. The oilfield has entered the late stage of high water cut period. Therefore, It becomes harder and harder to continue producing as much as before. The potential distribution analysis is base for further develop the oilfield.

Core data of Well La8-JP182 and Well Bei1–330-J49 were used to analyze the status and the distribution characteristic of the residual oil.

Core data of Well La8-JP182 were got before polymer driven. The analysis of the data revealed watered out status of the core. The Well La8-JP182 encounted three sets of oil reservoirs vertically, which are S, P, and G reservoirs respectively. All the layers in these three groups add up to 73.9m, among which 15.4m are not watered out, 4.9m are watered out slightly, 36.1m are watered out medially, and 17.4m are watered out heavily. In terms of percentage, they are 20.9%, 6.7%, 48.9%, and 23.5% respectively. There is 26.3% of thickness of S reservoirs layers unwatered out. That of G reservoirs is 37.4%. As for the P group, on the other hand, there is 3.91% of thickness that is not watered out. Threfore, the residual oil potential in S and G reservoirs are much richer than that of P reservoirs after water drive.

The total thickness of isolated untabulated reservoirs in this well is 26m, among which 22.7m are not watered out. The unwatered out thickness accounts for nearly 90% of the total isolated untabulated reservoirs thickness.

The Well Bei1–330-J49 was drilled after polymer flooding. The core data of this well indicates that more than 74.3% of total thickickness are watered out. Whereas, watered out layers are mainly concentrated in the PI2 payzone, while the other layers are washed slightly. After polymer flooding, there are still some potential to be tapped in relative thinner layers.

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