A Comparison Study between the Newly Developed Vertical Wells Steam Assisted Gravity Drainage and the Conventional SAGD Process

M Shirif,H Ibrahim,A Alarbah,E Shirirf

doi:10.4236/eng.2017.96036

Abstract

A numerical simulation study using the CMG-STAR Simulator was performed to compare the performance of the newly developed process (VWSAGD) utilizing vertical wells to enhance heavy oil recovery during steam assisted gravity drainage against the conventional steam assisted gravity drainage process which utilized horizontal wells (HWSAGD) under the same operating conditions. Two identical reservoir models were simulated for the two processes using 3-Dimensional, black heavy oil model (14° API). Each reservoir type consists of 49 × 49 × 20 grid blocks on a 5-acre model, which incorporated a typical heavy oil reservoir rock and fluid properties taken from the SPE case study, stspe001.dat (CMG 2015 release). A sensitivity analysis for both processes was performed for the grid density, soaking time, steam quality, bottom hole producing pressure, steam injection rate, reservoir thickness, reservoir area, and horizontal to vertical permeability anisotropy. More preferable reservoir conditions are those such as high horizontal to vertical permeability ratio, thick reservoir oil zones, as well as improved reservoir recovery for the VWSAGD process. Under unfavorable conditions such as thin reservoir oil zones, an improved reservoir recovery response was limited for the VWSAGD process and could be uneconomical in real field cases. Finally, the simulation results from this study include cumulative recoveries, Steam oil ratios, produced water-oil ratios, pressure and temperature distributions, and production rates. In addition, the results from this study have shown that the new VWSAGD process is more favorable than the conventional HWSAGD process.

Highlights

Over the past four decades, the conventional hydrocarbon reserves have declined rapidly
A sensitivity study was conducted to study the effect of the vertical permeability, reservoir area size, reservoir thickness, steam injection rate, steam quality, producing bottom hole flowing pressure, and the steam injection pressure
Optimization of Reservoir Perforation For the base run in this study, the reservoir thickness was selected to be 80 ft, and the question posed was what is the optimum perforation zone for the short injection string, and the long production string

Summary

Introduction

Over the past four decades, the conventional hydrocarbon reserves have declined rapidly. With an increase in the number of oil fields reaching economic limits and nearing maturity, new EOR recovery options are needed for reservoirs that are more challenging to produce, heavy oil reservoirs and bitumen. Heavy oil reservoirs contain a large amount of petroleum resources that have not yet been fully utilized. In Canada alone, it is estimated that there are over 750 billion barrels of heavy oil. The efficiency and economic recovery of heavy oil and bitumen deposits from these oil reservoirs are a major technical challenge. Steam injection technology has been used for many decades to improve the recovery of heavy oil. The main mechanism during steam injection is the reduction of oil viscosity and residual oil saturation by increasing the reservoir temperature. Effective methods are required in order to produce the heavy oil. A potential option for this is by the use of steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS)

Objectives

Methods

Results