A 16-in. section is one of the most challenging sections to drill in southeast Kuwait. The section consists primarily of highly interbedded carbonates, anhydrites, shale, and marl intervals, with significant variations in compressive strength that range from 3 to 25 kpsi. There are potential loss of circulation zones in the Tayarat and Dammam formations, which complicates the drilling performance, required flow rate, and other drilling parameters to be controlled. Bit balling of the cutting structure was expected in some intervals where water-based mud was typically used. The drilling assembly was a pendulum rotary design for vertical wells. A positive displacement motor (PDM) assembly is typically used in directional wells. In addition to the loss potential and long section interval, insufficient hydraulics and the high weight on bit (WOB) necessary in the Dammam to Ahmadi carbonates led to the premature failure of the cutting structure and bearings. A durable and reliable bit design was needed to drill the entire interval and the subsequent well to help reduce overall drilling costs. Collaboration between the operator’s drilling team and the bit supplier team resulted in successfully drilling a challenging 16-in. section and multiple additional wells. Rock types, performance, and compressive strength were analyzed using an advanced software program to determine the required design changes to develop the new tungsten carbide insert (TCI) bit. The goal of the new design was to improve hydraulics configurations, create durable and robust rubber seals, and design new advanced cutting structure materials. The new bit design provided exceptional performance in multiple wells in the 16-in. section in southeast Kuwait. The bit was used to drill three wells, with a cumulative footage of more than 9,000 ft in more than 240 drilling hours. Approximately two million revolutions were achieved with effective bearings and slight normal wear to the bit cutting structure elements. The new bit design helped to drill longer intervals and multiple wells with no risk of premature failure; it also helped to reduce drilling time and bit costs. A further test was implemented in directional drilling wells where the inclination was up to 50°.
Drilling a 16-in. section in southeast Kuwait presented several challenges. The formation is highly interbedded with significant variations in compressive strength ranging from 3 to 25 kpsi. Potential loss of circulation zones complicated drilling performance and required the flow rate and other drilling parameters to be controlled. Bit balling of the bit cutting structure was expected in some intervals where water-based mud was typically used. The drilling assembly was a pendulum rotary design. The variation in formation compressive strength and formation hardness in addition to the highly non-uniform lithology created high impact forces on the roller cone inserts. Additionally, insufficient hydraulics and the high weight-on-bit necessary in the Dammam to Ahmadi carbonates led to the premature failure of the cutting structure and bearings. A durable and reliable bit design was necessary for drilling the entire interval as well as the subsequent well to help reduce overall drilling costs. Collaboration between the operator's drilling team and the bit supplier resulted in successfully drilling a 16-in. challenging section and multiple additional wells. Rock types and compressive strength were analyzed using an advanced software program to determine the high-impact intervals and expected loss zones with insufficient hydraulics. Previous performances in the interval, as well as bit conditions, were thoroughly analyzed. These studies and finite element analysis were used to develop the new tungsten carbide insert (TCI) bit design featuring improved hydraulics configurations, durable and robust rubber seals, and advanced cutting structure materials. The design was dynamically tested in the laboratory in a similar application environment. The new bit design exhibited exceptional performance in multiple wells in the 16-in. section in southeast Kuwait. The bit was used to drill three wells with a cumulative footage of more than 9,000 ft in more than 240 drilling hours. Approximately two million revolutions were achieved with effective bearings and slight normal wear to the bit cutting structure elements. The new bit design helped drill longer intervals and multiple wells with no risk of premature failure and helped reduce drilling time and bit costs.
A 16-in. section of a well, located in the Great Burgan field of southeastern Kuwait, presents multiple drilling challenges. The section is approximately 4,000 to 5,000 ft long and is drilled through a highly interbedded formation that consists of carbonate, shale, and anhydrite. The carbonate typically generates impact damage, causing high levels of thermal degradation that affect the gauge inserts. In addition, lost circulation is a hazard commonly encountered during this application. The drilling of this section requires control of drilling parameters, specifically the flow rate. Failure to maintain sufficient flow rate results in poor cuttings transmission and insufficient cutting structure cooling that can create further performance complications. The challenge in this application is to drill the entire section with one bit run at a maximum rate of penetration (ROP). This paper describes a new tungsten carbide insert (TCI) drill bit design that helped to improve the drilling performance in this challenging section in different well profiles. This paper provides a detailed study of the challenging 16-in. section in Kuwait and discusses potential issues, problems, and solutions associated with the use of the new advanced roller cone design.
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