TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe primary objective of this work is to perform a complete characterization of the Womack Hill (oil) Field in Southern Alabama using petrophysical and reservoir performance data -and to provide reservoir management strategies that lead to improved oil recovery at Womack Hill Field. The process for achieving this goal requires the following specific objectives:l To develop correlations between the core and well log data in order to generate spatial distributions of reservoir properties such as: porosity, permeability, net pay, etc.
Bosque field presents some of the most challenging conditions for drilling, in Venezuela. The sandstone reservoir can be found below 20,000 ft, pressures exceed 12,000 psia, and temperatures are over 300°F. The main characteristic of this area is a great inverse fault in the north-south direction called Pirital's landslide. Because of this landslide, Cretaceous for-mations overlie a Miocene formation. These have been called the Aloctono block. So the geology is very complex, con-taining faulted structures, large dips, and hard and abrasive rocks. Drilling operations struggle to overcome numerous pro-blems, such as low rates of penetration (ROP), wellbore instability, lost circulation, and trajectory deviation. Since the discovery in 1988, these obstacles have seriously affected the field's profitability. To optimize the reservoir ma-nagement strategies, the operator Petroleos de Venezuela S.A. (PDVSA) commissioned a delineation and development project. A fundamental issue has been to improve drilling perfor-mance because of its notable influence on field development. To achieve this goal, a multidisciplinary drilling team was for-med, involving not only drilling experts but also personnel from other areas, such as production and reservoir engineers, geophysicists, geologists, and petrophysicists. To construct the first project's well, the team selected the well location by seismic 3D data, combining the reservoir objectives and the best conditions for drilling, determined the bottomhole assembly (BHA) with best vertical response by drillstring simulation, and used near-balance drilling and 65/8-in drillpipe to increase the ROP. These practices led to reach-ing a total depth of 21,199 ft, an ROP increase of 25% in the Aloctono block, and the largest Aloctono thickness drilled, 12,850 ft, to reduce the drilling time and the well-construction investment. A key factor was the 95/8-in casing run, which re-quired a new design and a detailed analysis of the rig and tools capabilities because of being the heaviest casing ever run in Venezuela (maximum tension of 1.25×106 lb). Introduction Bosque area covers approximately 29,500 acres, located approximately 300 miles east-south from Caracas, in the eastern basin of Venezuela1,2 (Fig. 1). The main characteristic of this area is the presence of a great inverse fault in the north-south direction called Pirital's landslide. Because of this landslide, Jurassic formations overlie Miocene formations. These Jurassic formations have been denominated as the Aloctono block. Drilling operations in the thicker part of the Aloctono block are very challenging, presenting numerous hurdles among them extremely low rates of penetration (ROP), wellbore instability, and deviated trajectories. In the 1990s, these factors affected drastically well-construction works. Drilling times were too elevated, which reduced the interest to develop this area. Because the high reserves estimated as 286×106 bbl and 1674×109 scf of oil and gas, respectively,3 a delineation and development project was assembled to optimize the reservoir management strategies. The team immediately recognized the need for improving the drilling performance to enhance wells' profitability. To construct the first well of the project (PIC-25), the drilling team focused on overcoming the Aloctono block's problems optimized the drilling practices. To reduce the de-viation problem, they used seismic 3D data to select the well location in an area of small dips and drillstring simulation to identify the BHA that provides the best vertical response, near- balance drilling in the Aloctono block section to increase the ROP, and 100% oil base mud to control wellbore insta-bility. All these factors, along with an adequate casing design and tight operations surveillance, led to reducing the drilling time and, therefore, increasing the well's profitability.
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