Summary The purpose of this study was to identify the most effective methods to free stuck pipe and to quantify the success rates of these methods under various wellbore conditions on the basis of historical data. This information has been integrated into a decision-making flow chart based on risk economics to determine when to begin and terminate operations to free stuck pipe. Introduction The Offshore Producing Div. at Texaco U.S.A. has developed a standard operational procedure for handling stuck pipe. The procedure involves spotting a diesel-based pill (DBP) if the pipe cannot be worked or jarred free in the first few hours after sticking. If the DBP fails to free the pipe after about 24 hours, the pipe usually is backed off above the free point and we try to free the pipe with fishing jars. Until now, we made these decisions without supporting data to indicate whether the benefits of operations to free stuck pipe justified the cost. Although the costs of pipe-freeing procedures usually are small compared with sidetracking costs, they are significant. Attempts to free stuck pipe by spotting pills or jarring usually require several rig days and can cost hundreds of thousands of dollars. These operations should be implemented only if their potential benefits outweigh their costs. The primary objectives of this study were to quantify the probabilities of success for various methods of freeing stuck pipe and to formulate a generic stuck-pipe decision-making process based on risk economics. When fishing operations begin, a certain cost is associated with freeing the pipe successfully, and a higher cost is associated with an unsuccessful fishing attempt that leads to plugback and sidetrack. This situation (two possible outcomes with known costs and known probabilities) lends itself well to expected value analysis. In this study, the expected cost of attempts to free stuck pipe is called risked fishing cost (RFC).

The cost effective philosophy of a drilling template has been applied to the development of Garden Banks 189 in the Gulf of Mexico. This paper describes the economics, design and installation of a simple drilling template for multiple sub sea exploratory/delineation wells. Methods to costs have operators. prior to program is reduce project development always been of interest to One of the methods employed completing the delineation the drilling template concept. An operator can drill multiple delineation wells through a drilling template to investigate a prospect. A template provides a means to accurately space-out future wells in relation to each other. If the prospect is commercial, a production facility (typically a platform) can be aligned and installed over the predrilled wells. These wells can be tied back to the surface and used as production wells. Savings are achieved in this development scheme because there are no expendable wells. Although attractive, the first prerequisite for a drilling template application is that the template site must be a suitable platform site. Typically, this location is not known after one exploratory well. Two or more delineation wells are normally required to pinpoint this location. For this reason, Texaco and other companies have not routinely benefited from this concept. In May 1989, a nine slot template was installed over the #1 discovery well in 718' of water at Garden Banks 189. Due to the circumstances, a unique template design and an unconventional installation procedure resulted. Since installation, two delineation wells have been drilled through the template and temporarily abandoned. Tiebacks of these 3 wells are scheduled immediately following the installation of the platform in 1991. PROJECT HISTORY In the fall of 1988, Texaco drilled one successful sub sea exploratory well in 718' of water at Garden Banks 189 (9B 189). Geographically, this block 1S located in the Gulf of Mexico 185 miles southeast of Houston, Texas. The straight hole #1 discovery well penetrated 169' of oil and 126' of gas pay from six intervals ranging from 5000' to 8500' TVD. Two of the oil zones were flow tested at 739 and 2037 BOPD respectively. The #1 well was drilled through a seismic bright-spot associated area in the southwest quadrant of GB 189 (Figure 1). This well is positioned 1200' south of an east/west shipping fairway which obstructs the entire northern half of the block. The southeast and southwest quadrants are geologically separated by a salt diaper. Severe seafloor irregularities exist throughout the south central region of the block over the salt diaper. Potential platform sites were limited to the southwest quadrant due to the confinements imposed by the fairway, seafloor irregularities, salt diaper, reserve locations and lease lines. The #1 well's location offered a suitable platform location based on preliminary mapping, the #l's results, a shallow hazard study and a drilling reach study. This site was operationally suitable because it permitted future platform wells to fully exploit the discovered bright-spot region and also allowed the capability of reaching into a potential wildcat bright-spot region to the northeast.

Summary This paper describes the economics, design, and installation of a simple drilling template that was used to retain or save subsea exploratory and delineation wells in Garden Banks Block 189 (GB 189) in the Gulf of Mexico. Introduction One way an operator can reduce project development costs is to drill multiple delineation wells through a drilling template to investigate a prospect. A template provides a means to space future wells accurately in relation to each other. If the prospect is commercial, a production facility (typically a platform) can be aligned and installed over the predrilled wells, which can be tied back to the surface and used as predrilled wells, which can be tied back to the surface and used as production wells. Cost savings are achieved in this development scheme production wells. Cost savings are achieved in this development scheme because there are no expendable wells. The first prerequisite for a drilling-template application is that the template site must be a suitable platform site. This location typically is not known after one exploratory well; two or more delineation wells are normally required to pinpoint the platform site. For this reason, Texaco and other companies have not routinely benefited from using drilling templates. In May 1989, a nine-slot template was installed over a discovery well (Well No. 1) in 718 ft of water at GB 189. The circumstances led to the use of a unique template design and an unconventional installation procedure. Since installation, two delineation wells have been drilled procedure. Since installation, two delineation wells have been drilled through the template and temporarily abandoned. Tiebacks of the three wells are scheduled to occur immediately after platform installation in Sept. 1991. Project History Project History In Fall 1988, Texaco drilled one successful subsea exploratory well in 718 ft of water at GB 189, located in the Gulf of Mexico 185 miles southeast of Houston. The straight-hole discovery well penetrated 169 ft of oil and 126 ft of gas pay from six intervals ranging from 5,000 to 8,500 ft true vertical depth. Two of the oil zones were flow-tested at 739 and 2,037 B/D, respectively. Well No. 1 was drilled through a seismic bright-spot area in the southwest quadrant of GB 189 (Fig. 1). The well is positioned 1,200 ft south of an east/west shipping fairway that obstructs the entire northern half of the block. The southeast and southwest quadrants are geologically separated by a salt diapir. Severe seafloor irregularities exist throughout the south-central region of the block over the salt diapir. Potential platform sites were limited to the southwest quadrant because of the confinements imposed by the fairway, seafloor irregularities, the salt diapir, reserve locations, and lease lines. Well No. 1's location was determined to be a suitable platform location on the basis of preliminary mapping, a shallow-hazard study, and a drilling-reach study. The site was operationally suitable because it would permit future platform wells to exploit the discovered bright-spot region fully and would platform wells to exploit the discovered bright-spot region fully and would allow directional reach into a potential wildcat bright-spot region to the northeast. The limited number of alternative platform locations in GB189 led to the investigation of using a drilling template. The final decision to use a drilling template was justified by a favorable economic analysis. In addition to saving future delineation wells, the drilling-template strategy had to incorporate the previously drilled discovery well. Therefore, a project goal was to finish the delineation program and develop GB189 with project goal was to finish the delineation program and develop GB189 with no expendable wells.