Abstract

This paper presents the reservoir considerations, implementation and results of a new completion technology with the aim to improve ultimate recovery. The non-uniform production profile across the horizontal hole especially in the highly heterogeneous and fractured reservoirs can result in premature water production and lower ultimate recovery. PLT surveys were carried out in some horizontal wells which indicated non-uniform production profile across the horizontal holes. Therefore the need for production system as part of the completion was raised to control water production and to improve ultimate recovery. This completion technique will the low and high permeability intervals to contribute to flow was found to be the optimum option for this highly heterogeneous and fractured reservoir.

Horizontal hole segmentation using ICD (Inflow Control Device) completion was found to be the optimum option to be tested as pilot in a new and an existing wells. The new well was expected to penetrate highly fractured area and the existing well is also located in highly fractured area.

The ICD Equalizer system was installed in both wells to evaluate the technique. The surface testing results of the re-completed well indicated a drop in the well water cut from 7% to traces. PLT survey was carried out in both wells and indicated uniform production profile across the horizontal section. Therefore the reliability of the technique was proved and these jobs were considered as the first application in United Arab Emirates. With field scale implementation, the reservoir simulation and economic analysis revealed an improved oil recovery of 1% and higher NPV.

Introduction

This paper presents the reservoir considerations, implementation and results of the new completion technology to improve ultimate recovery of an oil field in the United Arab Emirates.

Horizontal well technology has become an established method of drilling conventional wells due to their improved recovery efficiency, reservoir drainage and delayed undesirable fluids (water & gas). However non-uniform production profile across the horizontal hole especially in the highly heterogeneous and fractured reservoirs can result in premature water production. This may cause bypassed oil, lower ultimate recovery and therefore decrease in profitability.

The main characteristic of this reservoir is the presence of a complex fracture network within the highly heterogeneous matrix system. Both matrix and fracture systems play an important role in the production mechanism of the reservoir. Additionally, the reservoir is characterized by the presence of Sucrosic Dolomite rock (mainly in the South part of the middle reservoir unit) that significantly enhances matrix permeability further. Matrix permeability ranges from 0.01 mD to 12 Darcy with the average in excess of 100 mD. The fractures are described as fracture corridor system (or fracture swarms) that show two major trends, namely N40°E and N70°E. Fracture swarms/sub-seismic faults are structural features extending laterally over several hundreds meters and sometimes over several kilometers (Figure 1).

With water movement towards well-bore, sweep efficiency is affected and recoverable oil is impacted. This progress in well water cut and consequently field's water production increase will cause loss of production and reserves.

The shortening of well life cycle is directly linked to the well's water production and its source. In this field, once the well water cut reaches 50%, the constrained well production rate of 2,000 stb/d will no longer be maintained and the well has to be worked over or new wells to be drilled to be able to sustain the field production capacity. Therefore the need for a production system as part of completion strategy was raised with the aim to improve production efficiency.

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