Intelligent Wells: Horizontal-Well Simulation for Thin Oil Rims in the Niger Delta - A Case Study
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 133389, ’Intelligent Wells: Horizontal Well Simulation for Thin Oil Rims Abundant in the Niger Delta - A Case Study,’ by Obuekwe Mogbo, SPE, Total E&P Nigeria, prepared for the 2010 Trinidad and Tobago Energy Resources Conference, Port of Spain, Trinidad, 27-30 June. The paper has not been peer reviewed.

A simulation study was performed that illustrates the application of an intelligent horizontal well to an isolated reservoir with a thin oil rim in the Niger delta, Nigeria. Simulation of the intelligent well’s ability to simultaneously monitor and respond to reservoir conditions in two or more zones has proved to be a challenge for performance forecasting of such wells. Recently, intelligent wells have become used routinely both for their economic benefit and their advantages in accessing remote and difficult locations for workover during hydrocarbon exploitation. Furthermore, intelligent horizontal wells are being used to access remote thin-oil-rim formations that are abundant in the Niger Delta.   

Introduction

Because thin-oil-rim formations are plentiful in Nigeria, intelligent-well technology can be used in horizontal wells to maximize the value of these fields by delaying gas and water breakthrough. Also, Nigerian regulations do not allow commingling without the ability to back allocate production to each reservoir, thus limiting the application of intelligent-well technology to multiple/stacked reservoirs in the region.

This simulation study was carried out to justify installation of an intelligent well in a Niger delta field with a thin-oil-rim reservoir. The merit of intelligent vs. conventional production was addressed. A numerical reservoir simulator was used to model reservoir performance and production. Also, typical economic analysis for intelligent-well justification was performed. The results show that an intelligent horizontal-well completion is justified for this reservoir.

Background

Thin-oil-rim formations are on the order of a few to tens of meters thick and lie between water and gas layers. Often, they occur in reservoirs with lightly compacted sands having high porosities with permeabilities up to several darcies, and they commonly contain light oil. These properties culminate in favorable reservoir-flow conditions, reflected in a low drawdown required for production. However, these properties also can cause production problems, particularly water or gas coning, which can lead to early water or gas breakthrough.

Because of the small thickness of a thin-oil-rim reservoir, gas cusping and/or water coning will influence production and economic feasibility of the project, especially when permeabilities are high. Coning and cusping will happen when viscous forces (drawdown) exceed gravity forces. Less-than-optimal production rates can occur when trying to prevent critical drawdown for water coning and gas cusping. Excess gas production usually depletes the gas cap, reducing reservoir energy significantly, which leads to losses in ultimate recovery.