Perforating Unconsolidated Sands: An Experimental and Theoretical Investigation (2001)

Perforating Unconsolidated Sands: An Experimental and Theoretical Investigation Ian C. Walton; Ian C. Walton Schlumberger Search for other works by this author on: This Site Google Scholar David C. Atwood; David C. Atwood Schlumberger Search for other works by this author on: This Site Google Scholar Phillip M. Halleck; Phillip M. Halleck Pennsylvania State University Search for other works by this author on: This Site Google Scholar Luis C.B. Bianco Luis C.B. Bianco Petrobras S.A. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, September 2001. Paper Number: SPE-71458-MS https://doi.org/10.2118/71458-MS Published: September 30 2001 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Walton, Ian C., Atwood, David C., Halleck, Phillip M., and Luis C.B. Bianco. "Perforating Unconsolidated Sands: An Experimental and Theoretical Investigation." Paper presented at the SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, September 2001. doi: https://doi.org/10.2118/71458-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 Annual Technical Conference and Exhibition Search Advanced Search AbstractThis paper describes experiments and modeling undertaken to develop a perforating strategy for unconsolidated sand formations. The experimental program consists of single-shot perforations in cylindrical samples of three sizes (4-in, 7-in and 10.5-in diameters) of unconsolidated sand saturated with kerosene at residual brine saturation and placed under a high effective stress in a pressure vessel. The amount of sand produced during perforating, as well as that produced during post shot flow is measured and a video probe is used to observe post-shot sand production. CT-scan equipment is used to map the geometry of the cavity. The features of the sand behind the casing are examined and interpreted, providing essential insights into the interaction of the charge with the sand sample. A theoretical model of the failure mode of unconsolidated sands has been developed and supports the observations.The main results so far from this study are as follows:Perforating does not generate a tunnel in unconsolidated sands. The intense pressures set up in the weak sand sample by penetration of the shaped charge fluidize the sample and cause the initial tunnel to collapse.Production flow creates a dilated zone around the tunnel entrance. At a critical flow rate a large volume of sand is produced and the sample collapses. This occurs when flowing out of a hole in an unperforated sample as well.The implications of these results for future work and for field applications are addressed.IntroductionApproximately 90% of the world's oil and gas wells are drilled in sandstone reservoirs (although 60% of the oil and gas reserves are in carbonate reservoirs). Approximately 25 to 35% of the wells drilled in sandstone reservoirs experience some degree of sand production during their productive life. The key to maximizing the economic value of these wells is the ability to predict if, when, and how much sand will be produced and to determine and select the optimum method of controlling sand production while maximizing hydrocarbon production. In general, the industry has limited capability of optimizing completions in unconsolidated reservoirs. Operators are faced with uncertainties regarding whether these formations will produce sand, when, where and to what extent. Faced with these uncertainties, operators tend to adopt highly conservative sand control strategies (such as installation of gravel and screen), which traditionally have resulted in a significant amount of damage and complexity, at the most cash-flow sensitive time.An alternative to using sand control techniques is to complete the well in such a way as to minimize the risk of sand production. Over the last ten years substantial advances have been made in understanding the onset of sand production from weak, but consolidated, rocks (defined for this purpose as rocks that support a well-defined perforation tunnel). These advances have allowed a suitable perforating strategy to be defined.1 By contrast, very little is known about the sanding propensity of weaker rocks and there has been no attempt to develop a perforating strategy to minimize the risk of sand production. Usually it is assumed that sand will be produced at some point in the lifetime of the well and some form of sand control is immediately installed in anticipation of this.Only recently have experiments been performed to investigate the outcome of perforating very weak material. Wong et al.2 reported the results of an experimental program to investigate perforating unconsolidated sands under downhole conditions. They showed that there is no cavity behind the casing and collected some sand produced during perforating. However, the samples were not flowed to failure and therefore the stability of the samples could not be established. Snider et al.3,4 reported experiments on unconsolidated sand samples with zero confining stress. Keywords: upstream oil & gas, critical flow rate, cavity, sand production, diameter, completion installation and operations, kerosene, phillip halleck, strength, entrance hole Subjects: Perforating, Completion Installation and Operations, Completion Operations This content is only available via PDF. 2001. Society of Petroleum Engineers You can access this article if you purchase or spend a download.