An Investigation of Counter-Current Imbibition Processes in Diatomite

Abstract

An Investigation of Counter-Current Imbibition Processes in Diatomite D. Zhou; D. Zhou Chevron Petroleum Technology Company Search for other works by this author on: This Site Google Scholar L. Jia; L. Jia Stanford University Search for other works by this author on: This Site Google Scholar J. Kamath J. Kamath Chevron Petroleum Technology Company Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Western Regional Meeting, Bakersfield, California, March 2001. Paper Number: SPE-68837-MS https://doi.org/10.2118/68837-MS Published: March 26 2001 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Zhou, D., Jia, L., and J. Kamath. "An Investigation of Counter-Current Imbibition Processes in Diatomite." Paper presented at the SPE Western Regional Meeting, Bakersfield, California, March 2001. doi: https://doi.org/10.2118/68837-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Western Regional Meeting Search Advanced Search AbstractOil recovery from low permeability reservoirs is strategically important because of the large resources locked in such formations. Imbibition is fundamental to oil recovery from such reservoirs under most secondary and improved recovery processes of practical interest. It is also characteristic of porous medium wettability. The rate and the extent of imbibition depend critically on the viscosity of the wetting and nonwetting phases. In this study, we present our recent work on imaging imbibition in low permeability porous media (diatomite) with X-ray computed tomography. The viscosity ratio between nonwetting and wetting fluids is varied over several orders of magnitude yielding different levels of imbibition performance. We also perform a mathematical analysis of counter-current imbibition processes and develop a modified scaling group incorporating the mobility ratio. This modified group is physically based and appears to improve scaling accuracy of countercurrent imbibition significantly.IntroductionPetroleum production has, rightly, focused on the easiest to produce prospects. With more fields approaching maturity and abandonment, recovery options are required for more difficult to produce reservoirs such as low permeability diatomite and chalk formations. For example, estimates place the amount of original oil (OOIP) in the diatomaceous and siliceous shale formations of California at 12 to 18 billion bbl1. Although the volumes of oil in place are large, the low permeability creates challenging issues in producing this oil. Injectivity and productivity are generally low, and wells usually require hydraulic fracturing or in-place natural fractures to attain economic rates. Because of the limited injectivity, recovery processes must be designed carefully and natural oil-production forces optimized.In spontaneous imbibition, wetting fluid is drawn into rock by capillary suction and the non-wetting fluid is expelled. The rate and the extent of imbibition depend critically on the viscosity of the wetting and nonwetting phases. Other factors include: fluid/fluid interfacial tension (IFT), pore structure, the initial water saturation of the rock, and relative permeability curves. Water injection, steam injection, and CO2 injection in a water-alternating gas (WAG) fashion all rely to some extent on capillary imbibition to aid oil production. Steam injection is, for all practical purposes, carried out under saturated conditions with some fraction of the injected steam in the liquid phase. Likewise, initial heating of a cold reservoir is accompanied by condensation and flow of the resulting hot water away from the injector. In CO2 injection under both miscible and immiscible conditions, water slugs are usually injected with the aim of controlling CO2 mobility. Thus, capillary phenomena are important to most recovery techniques of interest in low permeability media.Imbibition can occur in a reservoir in both counter-current and co-current flow modes, depending on the fracture network and the water injection rates. Bourbiaux and Kalaydjian2studied co-current and countercurrent imbibition in natural sandstone samples. They reported significantly lower imbibition rates from counter-current experiments as compared to co-current experiments. They suggested that low counter-current imbibition rates are due to flow patterns and the extra viscous resistance generated when the two phases pass each other. They also observed some difference in final oil recovery from the two processes. Note that Bourbiaux and Kalaydjian2 use a single mineral oil (Soltrol 130, µnw=1.5 mPa-s) as the nonwetting phase in their experiments. They did not consider how different oil viscosities might change the imbibition rate and final oil recovery. Keywords: reservoir, wettability, core holder, flow in porous media, fluid dynamics, scaling, investigation, relative permeability, oil recovery, spe 68837 Subjects: Reservoir Fluid Dynamics, Improved and Enhanced Recovery, Flow in porous media This content is only available via PDF. 2001. Society of Petroleum Engineers You can access this article if you purchase or spend a download.