Application of Water-Based and Oil-Based Aphrons in Drilling Fluids

Abstract

Application of Water-Based and Oil-Based Aphrons in Drilling Fluids Frederick B. Growcock; Frederick B. Growcock M-I Search for other works by this author on: This Site Google Scholar Asif M. Khan; Asif M. Khan M-I Search for other works by this author on: This Site Google Scholar Gerard A. Simon Gerard A. Simon M-I Search for other works by this author on: This Site Google Scholar Paper presented at the International Symposium on Oilfield Chemistry, Houston, Texas, February 2003. Paper Number: SPE-80208-MS https://doi.org/10.2118/80208-MS Published: February 05 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Growcock, Frederick B., Khan, Asif M., and Gerard A. Simon. "Application of Water-Based and Oil-Based Aphrons in Drilling Fluids." Paper presented at the International Symposium on Oilfield Chemistry, Houston, Texas, February 2003. doi: https://doi.org/10.2118/80208-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 AbstractAphrons are specially stabilized micro-bubbles created in situ to aid in suppressing the loss of drilling fluid into high-permeability formations. Water-based aphrons are designed for aqueous drilling fluids, while oil-based aphrons are designed for non-aqueous fluids. In both cases, the micro-bubbles are composed of a core of gas or liquid stabilized by proprietary polymers and surfactants, which can aggregate to form a tough, elastic barrier to loss of drilling fluid in permeable zones. Some of these zones are typified by water-wet sands that are susceptible to fluid seepage and differential sticking. Others are characterized by laminated sand and shale sequences, which are expensive to drill with conventional drilling fluids or underbalanced drilling rig equipment.The authors describe how use of water-based and oil-based aphrons in drilling fluids can mitigate losses of drilling fluids downhole.IntroductionDepleted reservoirs in mature oil and gas fields are usually composed of water-wet sands. While the formations above and below these zones typically have much higher pore pressures and require higher fluid density to stabilize them, exposure of a depleted zone to this high-density fluid can result in significant loss of whole fluid and differential sticking. Both of these events are extremely expensive to correct. Uncontrollable drilling fluid losses are at times unavoidable in the often large fractures characteristic of these formations. Furthermore, pressured shales are often found interbedded with depleted sands, thus requiring stabilization of multiple pressured sequences with a single drilling fluid. Drilling such zones safely and inexpensively is very difficult with conventional rig equipment. Alternatively, one may try drilling underbalanced, but that also is fraught with risks which ultimately increase the cost of the operation significantly. A new drilling fluid technology was developed recently that does not entail drilling underbalanced, yet is designed to handle just those types of problems discussed above which often result from drilling overbalanced. This novel technology is based on the use of uniquely structured micro-bubbles of air. When incorporated in water-based muds, these micro-bubbles take the form of "water-based aphrons," while in oil or synthetic-based muds (OBM/SBM), they take the form of "oil-based aphrons." Water-based aphrons have been used successfully in various fluids to drill depleted reservoirs and other low-pressure formations in a large number of wells in North and South America.1 This technology has proved to be a cost-effective alternative to drilling underbalanced.In what follows, we will expand on laboratory studies presented recently that were undertaken to understand how water-based aphrons function to reduce lost circulation in high-permeability formations.2 In addition, we will introduce the OBM/SBM counterpart of this technology, oil-based aphrons.The Structure of AphronsWater-based and oil-based aphrons are composed of the same two fundamental elements:3a core that is usually fluid (gas or liquid) and which, as applied here, typically is air; anda protective shell. This shell is considerably different from a conventional air bubble, which is stabilized in a liquid medium only by a thin surfactant film.Aphrons are somewhat more complex. In Sebba's concept,3 water-based aphrons have two additional layers outside of that inner surfactant layer. As indicated in the rendition in Fig. 1, a sheath of viscosified water overlays the inner surfactant film, and outside of that is a bilayer of surfactants that ultimately renders the aphron hydrophilic and, therefore, compatible with the continuous aqueous phase. However, the structure of the bilayer is very fluid, i.e. the outermost surfactant layer in the bilayer is not strongly associated with the rest of the aphron. Consequently, water-based aphrons possess some hydrophobic/lipophilic character that is provided by the next-to-last surfactant layer. Indeed, the outermost surfactant layer tends to be shed when aphrons come in contact with each other. Keywords: spe 80208, surfactant layer, surfactant film, drilling fluid property, drilling fluid selection and formulation, jamin effect, society of petroleum engineers, application, concentration, drilling fluids and materials Subjects: Drilling Fluids and Materials, Drilling fluid selection and formulation (chemistry, properties) This content is only available via PDF. 2003. Society of Petroleum Engineers You can access this article if you purchase or spend a download.