Abstract

The objective of this study is to investigate the advantages of drilling horizontal wells on oil recovery improvement. To evaluate the effect of horizontal length, porosity, anisotropy, staggeredline well pattern with gas injection (in the top layer) and water injection (in the bottom layer), different scenarios were studied.

This study is focused on simulation of formation-A of a carbonate reservoir which consists of three layers; where horizontal well is going to be drilled in layer-2 of this formation. The average thickness of formation-A is about 167.64 meters (550 feet) and we also have tilted water oil contact in this formation.

This field has produced around 146.9 MMBBL until year 2002 for the last 12 years with the Recoverable Reserve of about 237.31 MMBBL. Up to now 40 wells have been drilled in this field.

IRAP/RMS software was used to generate geological model. Based on selected reservoir black-oil model, IMEX from CMG is used for simulation task. Sector model used for simulation as we only had one productive horizontal well in the formation (scale-down method).

This study confirms simultaneous use of overbalance method and horizontal well in this reservoir in order to:

  • Increase production rate up to 3 to 4.5 times by boosting productivity index (PI).

  • Communicate a large area leading to a better drainage area.

  • Postpone the water breakthrough by minimizing the draw down pressure.

Introduction

To identify the key factors controlling the impact of drilling new horizontal well at the reservoir scale are always a fundamental issue. Once this identification is done, simulation model will allow determination of which combination of vertical and horizontal wells will be the most suitable drilling activity in order to enhance the production. The impact of a horizontal well on the reservoir will depend on many factors. This includes the number of existing wells, well spacing, formation thickness, Kv/Kh, type of drive mechanism, completion intervals of vertical wells, well radius, drainage radius, oil viscosity (and other PVT properties) and obviously the length and placement of horizontal wells. The aim of this study is to assess effect of horizontal well performance on boosting oil recovery. A case study from one of Iranian reservoirs is simulated.

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