BRIDGING ADSORPTION OF CATIONIC POLYACRYLAMIDES IN POROUS MEDIA

Abstract

Bridging Adsorption Of Cationic Polyacrylamides In Porous Media K. Denys; K. Denys Institut Français du Petrole Search for other works by this author on: This Site Google Scholar C. Fichen; C. Fichen Institut Français du Petrole Search for other works by this author on: This Site Google Scholar A. Zaitoun A. Zaitoun Institut Français du Petrole Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Symposium on Oilfield Chemistry, Houston, Texas, February 2001. Paper Number: SPE-64984-MS https://doi.org/10.2118/64984-MS Published: February 13 2001 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Denys, K., Fichen, C., and A. Zaitoun. "Bridging Adsorption Of Cationic Polyacrylamides In Porous Media." Paper presented at the SPE International Symposium on Oilfield Chemistry, Houston, Texas, February 2001. doi: https://doi.org/10.2118/64984-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Conference on Oilfield Chemistry Search Advanced Search AbstractRecently, cationic polyacrylamides (CPAM) have been successfully applied in water shutoff treatments of oil and gas wells. These polymers adsorb strongly on reservoir rocks, building up an adsorbed layer of significant thickness. Moreover, under high rates, the coiled macromolecules stretch and can bridge large pore throats. This so-called bridging adsorption mechanism has been described previously for high-molecular-weight non-ionic polyacrylamides (PAM).CPAM rheology and retention behavior has been studied in unconsolidated SiC packs and in Berea sandstones in a permeability range 0.1–1 D with CPAM solutions having a cationicity between 0 and 50%. Due to the attraction between the positive charges carried by the polymer chain and the negative surface charges of the rock, both CPAM adsorption and bridging adsorption are higher than for PAM having the same molecular weight. A maximum adsorption is found around 10–15% cationicity. This maximum, observed both in SiC and in Berea, is due to the competition between adsorption energy and pore wall accessibility. Although the permeability to water drops considerably after CPAM bridging adsorption, the permeability to oil is remarkably preserved, which makes CPAM attractive for water shutoff applications.IntroductionOperators of mature oil and gas fields are often faced with a high water production coming from a water source (aquifer) or resulting from water injection. Excessive water production generally causes economic and operational problems. It decreases oil production, results in large amounts of water that need to be disposed and gives extra costs related to oil/water separation, handling and lifting. Other problems include the increased tendency for the formation of emulsions, scale and corrosion. So a high water production decreases the economical lifetime of a well and there is a need to reduce it. Classically the following distinction is made regarding the treatments to be used to tackle the water problem.1 If water and hydrocarbon zones are clearly separated, a permanent barrier, which is placed in the water producing zone, should be applied (Treatment A). Cements, resins or strong gels can form these full-blocking systems. If hydrocarbon and water zones are not clearly distinguishable or there is a high level of crossflow between layers, the use of total shutoff is risky. In this case disproportionate permeability reducers (DPR's), usually polymer solutions or weak polymer gels should be applied. The aim is to reduce water flow selectively while not influencing oil flow (Treatment B).1,2 The working of DPR's is based on the fact that adsorption of hydrophilic polymers can strongly decrease the relative permeability to water while having little effect on the relative permeability to oil.Due to the increasing need for bullhead treatments (treatments without zonal isolation), oilfield operators have focused on self-selective systems (Treatment B). These systems can be bullheaded downhole, reducing selectively the permeability to water with respect to the permeability to oil or gas. Due to this property polymers or weak gels were thought to be magic products that could be used in all situations. The relatively low success rate of DPR bullhead treatments (literature reports around 40%) shows reality is less favorable. Hereunder we will discuss three reasons for this by using an example of a DPR treatment on a two-layer well with 1/10 permeability contrast (Figure 1). Here the high-permeability layer is swept first, either by an active aquifer or by water injection. The low-permeability layer is still producing at high oil cut, although water production from the high-permeability layer is overtaking its oil production. Keywords: viscosity, experiment, permeability, relative permeability, polyacrylamide, cationic polyacrylamide, enhanced recovery, fluid dynamics, adsorption, permeability reduction 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.