Daño De Formacion

FORMATION DAMAGE DUE TO MINERAL ALTERATION AND WEnABILITY CHANGES DURING HOT WATER AND STEAM INJECTION IN CLAV-BEARING SANDSTONE RESERVOIRS

By
D. Brant Bennion, F .B. Thomas Hycal Energy Research laboratories Ltd

D.A. Sheppard SceptreResourcesLtd.
THIS PAPER IS TO BE PRESENTED AT THE 1992 SPE SYMPOSIUM ON FORMATION DAMAGE CONTROL TO BE HELD FEBRUARY 26-27, 1992 IN LAFAYETTE, LOUISIANAABSTRACT Detailed laboratory studies were conducted to study the effect of hot water and steam injection on the penneabillty, relative penneability, wettability, residual oil saturation and mineralogic composition and structure of a clay bearing sandstone reservoir in Southern Alberta, Canada. The san1)les initially contained only kaolinite and illite clays, classically classified as non-watersensitive. This paper presents the results of three detailed laboratory coreflow experiments and documents the degree of fonnation damage (up to 95% reductions in penneability were observed) due to temperature induced mineralogic and wettabillty alterations. Multipoint temperature tests from 32 to 265°C (90 to 510°F) were conducted at full reservoir conditions on preserved core material to generatethis data. The effect of steamflooding vs merely hot waterflooding at 265°C (51oaF)on residual oil saturation is also illustrated indicating up to a 20% additional reduction in res~ual 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 thedefinitive transfonnation 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 steamfloodingare 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 reservoir injection and production process, the ability tosuccessfully inject and produce the fluids is of 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 hotwater and stearnflooding are somewhat different processes than commonly associated with conventional wells. This paper will document some of the common causes of permeability i"1>8irment associated with thermal recovery projects and illustrate these phenomena using the results of a comprehensive suite of laboratory data.

MECHANISMSOF THERMALLY INDUCED
FORMATION DAMAGE

Formation damageoccurring during normal drilling,completion stimulationoperationshas been and
documented in the literature 1.2. This paper is concemed

with the mechanisms permeabilityimpairment of which can occur during a thermal stimulation operation.

These processeswould include: 1. 2. 3. 4. Mineral transformations Mineral solubilization/dissolution Wettability alterations In-situ emulsion formation.

Each ofthese damage mechanisms will now be discussed In greater detail. Mineral Transformations

solubility of quartzin the water phase and the presence of Ca, Mg or Fe in the injection fluid from direct Injection or solubilization of carbonate/dolomite cementing materials. The fluid which is in contact with the resulting newly formed swelling clay Is fresh steam condensate. Since the steam...