Paper: Field Tests to Determine Cement Bond Quality After Years of Production

The "RUFF-COTE" * process, a resin-sand coating applied to the external surface of casing to provide an improved bond between the casing and cement, has now been widely used in oilfield completions for the past ten years. This process has been applied to well casing from 2-7/ 8 in. slim holes to 20- in. surface casing in ultra-deep wells. Additional application has been on intermediate casing strings as well as on offshore platform jacket legs. Successful field usage of this process in thousands of wells has demonstrated its effectiveness in providing a good bond between the cement and casing. One area, however, that had not been previously evaluated was how long the initial cement-to-casing bond is maintained after well completions operations such as perforating, fracturing or acidizing, and normal stresses applied during production. In order to properly evaluate the resin-sand coating, it was necessary to analyze wells that had been completed both with and without the resin-sand coating and had been producing for a number of years. Continental's Sacatosa Field in Maverick County, Texas, fitted all requirements for a good field test. The Sacatosa Field located in South Texas produces from the shallow San Miguel sand at a depth ranging from 1300 to 1700 feet. The wells were drilled with a light water-base mud and completed with either 4-l / 2 in. or 5-l/ 2 in. casing. Casing was run to TD and cemented to the surface. A well plot of Sacatosa Field showing the test area is presented in Fig. 1. The casing was perforated with a single-plane horizontal jet gun consisting of either three or eight shots within 24 to 48 hours after cementing. All wells were then hydraulically fractured with a sand-oil treatment.