Recent Case Histories of Foam Drilling in Brazil

Abstract

Recent Case Histories of Foam Drilling in Brazil A.C.V.M. Lage; A.C.V.M. Lage Petrobras Search for other works by this author on: This Site Google Scholar E.Y. Nakagawa; E.Y. Nakagawa Petrobras Search for other works by this author on: This Site Google Scholar A.A. de Souza; A.A. de Souza Petrobras Search for other works by this author on: This Site Google Scholar M.M. Santos F. M.M. Santos F. Petrobras Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Latin America/Caribbean Petroleum Engineering Conference, Port-of-Spain, Trinidad, April 1996. Paper Number: SPE-36098-MS https://doi.org/10.2118/36098-MS Published: April 23 1996 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Lage, A.C.V.M., Nakagawa, E.Y., de Souza, A.A., and M.M. Santos F. "Recent Case Histories of Foam Drilling in Brazil." Paper presented at the SPE Latin America/Caribbean Petroleum Engineering Conference, Port-of-Spain, Trinidad, April 1996. doi: https://doi.org/10.2118/36098-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 Latin America and Caribbean Petroleum Engineering Conference Search Advanced Search AbstractSince 1994, Petrobras has been testing stable nitrogen foam to drill a series of wells in low pressure oil production zones. In the first tests, the operations were conducted under both situations, overbalanced and underbalanced with the main purpose of accessing the operational feasibility and the economic benefits of such drilling technique. This work analyzes information available after these tests, based on some relevant aspects;well productivity;drilling performance;economic advantages; andneed for further developments.Two vertical wells were drilled in Carmopolis Field, one overbalanced and the other underbalanced. The initial results have shown that the productivity improved substantially (almost four times) compared to a conventionally drilled well. In the beginning of 1995, a third well was drilled in Candeias Field, in a fractured carbonate reservoir. In spite of loss of circulation being the most common drilling problem in the area, the well was successfully drilled overbalanced. The increase in penetration rate was significant, bringing about a reduction in the overall drilling costs. Because of such encouraging results, Petrobras is planning to reenter the Candeias Field well and drill three short radius horizontal underbalanced wells until the end of this year.Finally, at the end of 1995, foam was also applied in an exploratory well in Parana Basin, where two high permeability and low pressure sandstone reservoirs were drilled, reducing formation damage. As the reservoirs were just below a thick layer of basalt, it was observed that foam drilling has twofold penetration rate in such hard rock.Despite the observed operational and economical viability, some crucial topics still demands intense R&D efforts.IntroductionIn 1994, Petrobras decided to re-evaluate operational and economical benefits of nitrogen foam drilling through some field tests. The bases for this decision were some recent technological advances in this area and the existence of many potential applications in low pressure and depleted reservoirs.As reservoir pressure in several oil fields has dropped to levels below water hydrostatic pressure, conventional drilling with water based mud is no longer appropriate. The large overbalance pressure favors filtrate invasion and the movement of solids, plugging the pore spaces in the rock around the wellbore. Such drilling conditions lead to formation damage and loss of well productivity. Moreover, conventional drilling fluids provoke loss of circulation in some depleted or fractured reservoirs. When it happens, drilling operations become problematic and the costs increase greatly.Thus, considering those scenarios, foam drilling appears as a valuable choice. It reduces the hydrostatic head of the drilling fluid column, making possible to drill in a balanced or underbalanced condition. The proper application of this technology prevents some of the problems related to fluid or solid invasion, reduces dramatically formation damage and eliminates loss of circulation1.Furthermore, the reduction of the bottom hole pressure also increases drilling rate and bit life1,2. Several foam drilling applications focus exclusively on those advantages, which provide operational time savings. It is particularly beneficial for drilling hard rocks because the gains are meaningful in comparison to the conventional drilling technique, even considering the additional costs of the whole nitrogen system.The first field tests were in Carmópolis, an old and depleted oil field with a heterogeneous conglomerate reservoir, which is supposed to be intensely damaged when drilled conventionally. Depending on the well location, usual drilling fluids cause total loss of circulation. Considering studies that indicated foam drilling as the technique with better chances of overcoming such problems, the company decided to drill two directional wells in Carmópolis using N2 fluid. Keywords: spe 36098, injection rate, nakagawa, souza, foam drilling, conventionally, reservoir, drilling rate, formation damage, productivity Subjects: Drilling Operations, Drilling Fluids and Materials, Formation Evaluation & Management, Drilling fluid management & disposal, Drillstem/well testing This content is only available via PDF. Copyright 1996, Society of Petroleum Engineers Inc. You can access this article if you purchase or spend a download.