Abstract

Detailed laboratory studies were conducted to study the effect of hot water and steam injection on the permeability, relative permeability, wettability, residual oil permeability, relative permeability, wettability, residual oil saturation and mineralogic composition and structure of a clay bearing sandstone reservoir in Southern Alberta, Canada. The samples initially contained only kaolinite and illite days, classically classified as non-water sensitive. This paper presents the results of three detailed laboratory coreflow experiments and documents the degree of formation damage (up to 95% reductions in permeability were observed) due to temperature induced mineralogic and wettability alterations. Multipoint temperature tests from 32 to 265 deg. C (90 to 510 deg. F) were conducted at full reservoir conditions on preserved core material to generate this data. The effect of steamflooding vs merely hot waterflooding at 265 deg. C on residual oil saturation is also illustrated indicating up to a 20% additional reduction in residual oil saturation by steamflooding. A complete suite of pre and post test petrographic studies on each sample tested including x-ray diffraction, thin section and scanning electron microscope analysis indicate the definitive transformation of inert kaolinite clay into water sensitive swelling smectitic clay due to reactions between the kaolinite clay and the quartz during the high temperature flooding process. The results of this study have specific application to the design of hot water and steam injection projects in other similar types of sandstone reservoirs.

Introduction

Hot water and steamflooding are commonly used techniques to mobilize and recover substantial additional low and mid API gravity oil from shallow hydrocarbon bearing formations. The input of thermal energy into the reservoir reduces the viscosity of the oil and Increases the reservoir energy allowing mobilization and production of the crude oil. As with any type of production of the crude oil. As with any type of reservoir injection and production process, the ability to successfully inject and produce the fluids is of paramount importance. Formation damage in the paramount importance. Formation damage in the reservoir can greatly reduce injectivity into the formation. if the thermal process is of a cyclic nature, the productivity of the formation on the production cycle can also be adversely affected and result in an overall reduction in the fraction of recoverable oil. Formation damage mechanisms during hot water and steamflooding are somewhat different processes than commonly associated with conventional wells. This paper will document some of the common causes of paper will document some of the common causes of permeability impairment associated with thermal permeability impairment associated with thermal recovery projects and illustrate these phenomena using the results of a comprehensive suite of laboratory data.

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