Effect Of Clay Swelling On Reservoir Quality

Abstract

Clay swelling affects not only reservoir quality but also many aspects of drilling operations in conventional oil production and in enhanced oil recovery. The focus of this paper is to characterize the swelling behaviour of smectites in direct contact with reservoir solutions. Two types of clay swelling are identified: crystalline swelling and osmotic swelling. Osmotic swelling is the major cause for permeability reduction due to smectites in hydrocarbon reservoirs. An X-ray diffraction cell was developed and used to quantify the swelling sensitivity of the smectites. In this method, a claywater mixture is X-rayed so that the effeCt of solution composition on clay swelling can be determined directly. Smectite swelling is very sensitive to the composition of fluids with which it contacts. The magnitude of swelling was found to be inversely proportional to ionic strength and depends on the dominant cation in system. New data collected for mixed electrolyte solutions shows that smectite swelling is not linear but a complex function of both ionic strength and cation ratios. The experimental data obtained allow us to construct a set of swelling diagrams for montmorillonite and other swelling clays. These swelling diagrams can be used to evaluate the effect of swelling clays on reservoir quality. Introduction Clay swelling has been long recognized as one of the major causes for formation damage in hydrocarbon reservoirs. In conventional hydrocarbon production, most of the clay related problems occur in the near well region, and are associated with well operations (drilling, completion, workover, etc.). Krueger(l) has provided an excellent review on this subject. In enhanced oil recovery (EOR), the potential for formation damage to occur is in many instances much greater because incompatible injection fluids often cause clay swelling or fines migration and thus impair the formation permeability. Even formations which do not contain smectite can have smectite-related formation damage because smectite clays can be synthesized through mineral/fluid reactions during thermal recovery(2,3). The formation of smectite was responsible for the reduction in porosity, permeability, and oil recovery rate at the Great Plain Pilot Project, Cold Lake(4). It was also partly responsible for the low steam sweep at the Ipiatik Heavy Oil Pilot, Cold Lake(5). Coreflood experiments have been used to characterize the effect of clay swelling on reservoir quality(6,7,8,9). In the coreflood experiments, a decrease in permeability (or an increase in injection pressure) is used as a measure of formation damage. However, a fair amount of core, which is not always available, is required to run coreflood experiments. In addition, coreflood experiments can be expensive. In this paper, we will introduce a relatively simple X-ray diffraction (XRD) method to quantify the clay swelling. This method requires a small amount of sample and offers an alternate tool to coreflood experiments in characterizing the effect of clay swelling on reservoir quality. Theoretical Basis of the XRD Method Swelling clays include two groups of layer silicate: smectites and vermiculites.

Detrimental Effect of Temperature on Fines Migration in Sandstone Formations

“…In conventional oil production, most of the clay related problems occur in the near well region, and are associated with well operations such as drilling, completion, workover, etc. Incompatible injection fluids often cause clay swelling or fines migration and this impairs the reservoir permeability (Zhou et al 1996). Clay particle migration is the most important mechanism of permeability reduction, since Berea sandstones containing very little or no swelling clays and a considerable amount of migratory or dispersible clays such as kaolinite and illite, which are sensitive to sudden changes in salinity (Khilar and Fogle 1983).…”

Stabilization of Mineral Suspensions by Guar Gum in Potash Ore Flotation Systems

“…Generally, clay particles swell the most in distilled water and the interlayer spacing decreases as the electrolyte concentration increases. Although there are no published data on clay swelling at ionic strengths higher than 0.5 mol/dm 3 , all indications are that the interlayer spacing for a number of clay minerals does not decrease any further above that concentration (Zhou et al, 1996). Therefore, in the case of CMC adsorption, two simultaneous phenomena take place as the ionic strength increases: the degree of clay swelling decreases and the size of the coiling CMC macromolecules decreases.…”

“…For illite suspensions, the range of the GG concentrations over which fl occulation occurs becomes much wider with increasing brine concentration. For dolomite suspensions, the GG concentration range for good fl occulation is broadest in water, and, then narrows as solutions (Theng, 1982) and the extent of swelling is a function of ionic strength and the type of the background electrolyte (Greenland, 1963;Zhou et al, 1996). A few years ago, the Ward's illite sample was tested in this lab using both BET and the "wet" procedure (Laskowski, 1996).…”

Effective Strategies for Selection of Suitable Clay Stabilizers to Control Clay Swelling

“…They are applied for pH and salinity control during steam injection and can be used to treat the whole formation. However, they are less effective compared with the other types of clay stabilizers [33][34][35][36]. Simple organic compounds are similar to simple inorganic compounds and are used in water flooding, workovers or pretreatment.…”