Abstract

The paper introduces some problems that subdivision injection and production technology is facing in the stage of extra-high water cut production in Daqing Oilfield, the problems have become main factors affecting sustained development of Daqing Oilfield, like subdivision water injection, separate layer fracturing in thin restraining barrier and injecting surfactant to reduce pressure problem, each of them is close to challenge technical limit.

Introduction

Daqing Oilfield is a giant, heterogeneous, multilayer sandstone oilfield with 80–120 small layers, interlayer permeability difference of over 60 times. After having developed for 42 years, Daqing Oilfield has performed a miracle of keeping stable production of 50 million ton for 27 years. Till the end of 2002, field-wide recovery factor is up to 47.2%, 50.4% in La-Sa-Xing reservoirs. Daqing Oilfield has entered into extra-high water cut development period, oilfield development will face many contradictions. From the eye of an oil production engineer, in extra-high water cut development period, the development difficulty of oil production technology will increase greatly, and two nagtive influence factors will be faced: Firstly, new and old contradictions make the difficulty of oil production technology increases greatly, it's difficult for the current technology to suit for the continuous change features of field development; secondly, the personality of technology makes adaptability of technology drop obviously, some technologies for medium-high water cut development phase have exposed some inadptabilities, which brings some challenges to technical limit for oil production engineering.

Challenge 1: Subdivision Separate Layer Production and Water Injection Technology
The effects of separate layer injection and production

With the improvement of geological research and development degree, the requirements to water injection are also higher than before. The development of water injection technology in Daqing oilfield experienced the following four processes:

  1. Commingled water injection,

  2. concentric injection,

  3. eccentric injection, and

  4. integrated injection.

Through the above improvements, the development technology improved quickly:

  1. The struck distance of separate layer is reduced from over 8m to 2m.

  2. The average time of testing and allocation per well is reduced from over 7d to 2d that also cuts the cost.

  3. The testing accuracy is improved with direct measurement than with successive subtraction method.

  4. Through separate layer injection, interlayer contradication is eliminated which also meets the requirement of reservoir engineering, makes it possible for subdivision separate layer production.

The application of commingled water injection

Before 1964, according to the development strategy aimed at keeping a stable reservoir pressure and commingled water injection was applied. And water flushing and experimented injection technologies were developed which ensured the water was injected into all kinds of reservoirs and the reservoir intook the water in a certain degree. As the result, the oilfield kept a constant natural flow capability in the early stage.

The application of separate layer injection and production
Low water cut period

After 1964, the problem of commingled water injection emerged that water breakthrough occurred in the interlayer, interval and horizontal directions very quickly. In order to control the rate of water breakthrough, a series technologies and tools were developed, for example, the hydraulic expandable packer and Model 745–4 fixed water flow regulator. The seprated water injection technology was formed including sealing inspection, channeling inspection, snubbing operation and zonal testing techniques. Because Model 745–4 fixed water flow regulator couldn't adjust water injection rate repeatly, a Model 655 removable water flow regulator was developed which consisted of mandrel and removable core, adjusting the water injection rate by changing the size of nozzle of removable core which realized 4 layers' water injection in a single well.

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