Innovative Drilling Technology Reduced Drilling Time in Deep Drilling Jurassic 16in Hole Section-Case Study

Changning shale gas block is located in the southern part of the Sichuan basin. It is one of the first pilot experimental shale gas blocks in China. The paper will elaborate the drilling challenges in the field and the overall drilling performance with conventional approaches. In 2014, new drilling tools and methods were tried and applied. These significantly improved the performance, further elevating the drilling speed to a new level.The paper will review the drilling performance of horizontal wells completed previously in the field. It will focus on demonstrating formation characteristics, well trajectory and geometry design, drill bit and directional bottomhole assembly (BHA). One of the biggest challenges is the hard rock on top of the shale formation that constrains the drilling speed, especially when designing the curve interval at the hard rock. By analyzing the drilling challenges, a new drilling system and method were introduced to the project in 2014 to combat the challenges. It has been proven successfully with actual drilling data.Initially, as a pilot project, conventional motor technology was applied to six horizontal wells in Changning block. The average well drilling cycle was approximately 66 days for 1000 m of lateral section. The main challenge with motor drilling was high drag at the curve and lateral due to extreme friction as high mud weight was applied to balance the formation stability. This resulted in a poor on-bottom penetration rate during sliding mode. Directional work at the hard rock formation posed an additional challenge. In early 2014, a hybrid high-build-rate rotary system was applied to deepen the kickoff point and avoid the steering work in the hard zone. Air drilling was used to drill vertically across the hard rock. A power rotary steering system was also implemented to further improve the drilling speed in the lateral section. The combination of technical approaches led to significant drilling improvement. The rate of penetration (ROP) on bottom at the curve section has improved 200% over conventional drilling. The well drilling cycle was cut in half, which was considered as a breakthrough achievement in the field.With the application of hybrid high-build-rate rotary steering system, the new well design can be executed. Air drilling is chosen to drill through the hard rock in the shortest distance. Using the power rotary steering system for the lateral further promotes the drilling performance to a new level.

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Challenging Conventional Best Practices with an Updated Productive Drilling Solution

Al-Majed

Soh

Ali

et al. 2018

All Days

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Among the challenges facing an operator while drilling offshore in the Middle East are the 16-in. sections of wells where highrisk of losses and torque and drag limitations force the operator to be extremely conservative during the planning stage. Operator objectives for this particular interval normally call for mitigating any high-potential incidents, which is driven by the past experiences as well as decades of old best practices. The approach used in the past has been to drill with a positive-displacement mud motor and weighted mud until losses are experienced, and then switch to mudcap drilling to maintain hydrostatic while drilling. The positive displacement mud motor efficiency is excellent in lower inclination wells but deteriorates once the inclination exceeds 30n, leading to significantly lower penetration rates and extending the openhole wellbore exposure time. This prolonged openhole time exposes the bottomhole assembly and wellbore to the same risks the operator has always attempted to avoid. A service provider evaluated the drilling method with the objective of reducing the drilling time and drilling risks. Drawing from offset well experiences and the conditions of successful operations, a motorized rotary steerable system (RSS) was proposed to the operator. Time and cost analysis were performed, showing that improved hydraulics and drilling dynamics would result in significanttime savings and should be compounded as the 16-in sections are drilled in batches of up to seven wells. The operator implemented the recommended BHA and parameter design for the remaining seven wells, resulting in up to a 120% increase in the average rate of penetration by the motorized RSS over conventional positive displacement motors. The accompanying benefits to the operator included increased hole cleaning capacity, torque and drag reduction in tripping times, and reduced risk exposure in the 16-in. sections. The results obtained with the updated design demonstrated that in the current challenging energy market environment, using proven technologies to challenge decades of best practices can bring significant benefits to the well construction and enhance the performance benchmarks for future wells.

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Innovative Drilling Technology Reduced Drilling Time in Deep Drilling Jurassic 16in Hole Section-Case Study

Cited by 3 publications

References 17 publications

A prediction model of the shortest drilling time for horizontal section in extended-reach well

A prediction model of the shortest drilling time for horizontal section in extended-reach well

Drilling Evolution in Changning Shale Gas Block of Central China

Challenging Conventional Best Practices with an Updated Productive Drilling Solution

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