Zeng, Yie; Inst. of Porous Flow and Fluid Mechanics; Wang, Jianshe; Research Inst. of Petroleum Exploration and Development; Huang, Yan Zhang; Inst. of Porous Flow and Fluid Mechanics; and Liu, Wenzhang; Petroleum Exploration and Development Petroleum Exploration and Development Copyright 1989, Society of Petroleum Engineers, Inc.

Abstract

Many heavy oil reservoirs in China are charactered with multi-layer horizons with barriers in between of them. During steam injection those very tight clay layers act as heat absorbing media with heat conductivity varies with the changing of aqueous saturation and as barriers against steam transpiration and/or penetration. However, very few works have been done on this subject, and the consequent effect on steam injection remained unknown.

In this work, started with brine/air capillary pressure curve measurement of the barriers at pressure curve measurement of the barriers at different temperature by vapour pressure desorption method, relative permeabilities were calculated, which would be otherwise extremely difficult to be obtained by conventional approaches if is not impossible.

Overall effects of barriers on steam stimulation and steam flooding were studied by numerical simulation based upon the experimental data on the effects of: absolute permeability; capillary force; barrier distribution; and heat loss. Results from simulation suggested that capillary forces of the barriers contribute about 7% increase in terms of heavy oil production, oil steam ratio and recovery efficiency. production, oil steam ratio and recovery efficiency. Attempts of explanation of these positive influence were made.

Introduction

Many heavy oil deposits have been discovered in China such as those in Shengli, Liaohe and Karamay oilfields. Steam stimulation and flooding have been adopted in industrial scale which proves to be effective methods. Some of the heavy oil reservoirs are charactered with multi-layer with intercalated barriers in between.

However, in previous studies, less attention was payed on the characteristics of the intercalations and payed on the characteristics of the intercalations and their effects on steam injection. Nevertheless, and net pay to total thickness ratio 0.5 or higher is taken by pay to total thickness ratio 0.5 or higher is taken by many people as a rule of thumb in evaluating feasibility of steam injection. In numerical simulation usually only fixed heat transfer coefficent and capacity are considered. The effects of barriers as porous media and the effect of their distribution on steam injection still remain to be investigated.

Intercalations are very tight or weak permeable non-oil bearing clay formations. During the process of steam injection, those barriers absorb and transmit the injected heat; separate and/or isolate the hot fluid. The physical nature and geometric configuration distribution of intercalations will then affect the overall production and other important parameters. Especially in steam injection on parameters. Especially in steam injection on multi-layer heavy oil reservoir, the above influence can never be neglected. To in-depth study the effect of intercalation on steam flooding, the following questions need to be answered :

  1. As very tight porous media, if the most important flowing curves porous media, if the most important flowing curves of the intercalation are measurable and whether they would be significant on over all simulation result.

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