Steam Zone Growth During Multiple-Layer Stream Injection

Abstract

Abstract The development of multiple parallel steam zones of equal thickness and uniform separation is described mathematically. At small times, the growth of one of the steam zones is independent of the presence of the orders. At long times, simple relationships are obtained which describe the growth of the steam zones. Generally, it is found desirable to allow steam to penetrate the underground reservoir at a number of vertical positions if sufficient steam-generating capacity is available to maintain comparable injection rates in all the layers. If a limited steam-generating capacity is available, the larger steam zone volume is created in the single-layer system. Introduction The use of hot fluid injection as a means of lowering oil viscosity in petroleum reservoirs is becoming increasingly common. Prominent among the thermal techniques being used is steam injection. The basic mechanisms involved when steam flows through oil-containing porous rock have been reported by Willman et al. The growth of the steam zone when steam enters a single layer at constant injection rate has been developed by Marx and Langenheim. Frequently, an underground formation is stratified and presents a number of horizontal paths for the injected fluid to follow. This paper considers the steam zone development when a large number of highly permeable paths of equal thickness, separated by arbitrary but equal distances, are available for flow of injected steam. THEORY Consider the system shown in Fig. 1. A number of horizontal zones of equal thickness, hs are separated from each other at distances 1. It is assumed that there are infinitely many layers in the vertical direction. Further, important assumptions of the mathematical model to be employed are as follows.Steam enters all the layers at constant and equal rates.Steam zone temperature remains constant throughout the steam zone at the value of the input steam temperature.The heat capacity of the steam zone may be represented by some average value.Heat loss occurs normal to the horizontal boundaries of the steam zones.No heat is transported by conduction or convection ahead of the steam front. The formation immediately ahead of the steam zone remains at original reservoir temperature. The shape of the temperature distribution will then be that of a step which moves outward.At each position in space the fluid and rock temperatures are equal. STEAM ZONE LAYER OF FINITE AND NONZERO THICKNESS SPEJ P. 1ˆ