Published: 11/01/2011
Published: 11/01/2011
Located south of Monagas, Venezuela, the Orinoco Belt holds reservoirs composed of unconsolidated sand and heavy oil. Accessing production zones in this area required PDVSA to drill lateral sections in reservoirs 7 to 30 m thick and 4,700 to 5,200 m long. And, inclinations in these sections can reach 90° resulting in a low annular velocity, which allows cutting beds to form. Beyond the fluid used to remove these cuttings, holes must be backreamed at least twice to clear cuttings from one of these sections.
Lateral sections are drilled with 8 1/2-in PDC and completed with slotted liners. And, although the sandstone UCS is below 3,000 psi, the long intervals that must be drilled and backreamed by the bit, erosion from turbulent flow, grain size, geometry, and bit flow distribution were all shortening bit life. Faced with an unacceptable cost per foot, the operator reasoned that to remain economically viable a bit was needed that could endure the conditions in this application and drill at least 4 sections.
To provide a cost-effective bit for the operator, a Smith Bits design team researched dull analysis from the operational area. Based on this information, they concluded that a bit for this application could be optimized by making two significant changes: First, they changed the hydraulic configuration of the drill bit by blanking off its outer nozzles, while leaving the center nozzles open. This redirected mud flow away from the bit body and to the formation, which reduced the erosive hydraulic force that was hitting the bit's blades and compromising their durability. And to further increase durability, their second change involved altering the abrasion resistant matrix powder in the bit's blades. To select an application-specific bit, the team used IDEAS integrated drillbit design platform. The resulting bit model indicated that a PDC bit was needed with a more aggressive cutting structure: the 8 1/2-in MDi619LBPXX.
The optimized PDC bit proved to have much greater durability than previous bits and, as a bonus, steering response was improved. The first 8 1/2-in MDi619LBPXX PDC bit drilled four lateral sections totaling 4,267 m, saving USD 38,500. The second bit drilled six lateral sections totaling 6,095 m, saving USD 77,000.
Challenge: To reduce drilling costs, find a bit that is capable of drilling four or more highly abrasive lateral sections.
Solution: Run two 8 1/2-in PDC bits with increased abrasion resistant matrix material and optimized hydraulics.
Results: The first bit drilled four laterals: totaling 4,267 m, saving USD 38,500. The second bit drilled six laterals: totaling 6,095 m, saving USD 77,000.
