Abstract

It is usually very difficult to match the system of naturally fractured reservoirs, especially to predict the oil production and to determine appropriate production operation methods. And accordingly, very few naturally fractured reservoirs are optimally developed worldwide. S74l fault block, a naturally fractured reservoir consisted of igneous rock in China, was scheduled to put into production with both vertical and horizontal wells. One objective of this work is to describe the process of making the optimal field development strategies by integrated technology on the basis of evaluating inflow performance in terms of introducing a novel approach with production testing data.

Also presented are theoretical models of comprehensively decision-making production operation methods, which have been successively applied to thirty-odd reservoirs or fault blocks. The models were developed by incorporating reservoir geologic research, reservoir engineering scheme, production performance and surface facility performance to model the future production performance of oil producers under different conditions in S74I fault block It is shown that the formulas of evaluating inflow performance can be easily applied to the field and there exists good agreement between the prediction results and field data, and that gas lift, electric submersible pump and sucker-rod pumping can be efficient artificial lifting methods under different conditions for vertical and horizontal wells.

Introduction

There exists great difference between naturally fractured reservoirs and homogeneous reservoirs on the aspects of geology, rock physics, production and economy. And also it is usually very difficult to match the system of naturally fractured reservoirs, especially to predict the oil production, not to mention to determine appropriate production operation methods. In the naturally fractured reservoirs, the influence of rock compaction and inertial flow resistance are two major factors influencing the well inflow performance(1,2), but seldom included for evaluating the inflow performance(3).

According to developing practices of oil fields, it is shown that choosing appropriate production operation methods will have a strong positive influence on the ultimate recovery(4). And accordingly, we incorporate reservoir geologic research, reservoir engineering scheme, reservoir numeric simulation, production performance and surface facility performance before the production schedule into scientifically decisionmaking on the would-be production operation methods, which should be technically feasible, economically rational and objectively permissive on the macroscopic scale. The basic models of production operation methods presented in this paper have been applied to thirty-odd reservoirs in China, and the applied results shown that the models are both effective and scientific. With introducing a novel approach of evaluating well inflow performance in naturally fractured reservoirs, which combined the influence of rock compaction and inertial flow resistance, we developed the theoretic models for the purpose of providing reliable information for proving and decision-making the production operation methods.

BACKGROUND

S741 igneous rock reservoir, a naturally fractured reservoir, is rich in hydrocarbon and located in the middle of Huiming surrectic structure center. The major payzone buries 3400m under ground and its original reservoir pressure is 35.3MPa 37.13MPa, bubble point pressure 19.86MPa - 22.05MPa, fonnation pressure coefficient 1.02-1.09, reservoir temperature l30CJ-1380 and geothermal gradient 3.760/l00m.

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