No abstract

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.

In the past year, a client in the Arabian Gulf has been increasing appraisal and development well activity from the same slot to reduce the uncertainty of reservoir depth, identify oil-water contact, and determine reservoir production strategy. The operator has been addressing these issues by drilling pilot sections from planned development wells, then plugging and abandoning the section prior to drilling the production lateral. The sidetracking operation is then performed from the previous casing shoe, aided by cement plug and landed to the required horizontal depth provided by the data from pilot section. Conventionally, positive displacement motors (PDM) have been used to perform the sidetrack effectively, then followed by a rotary steerable system (RSS) in the bottom hole assembly (BHA) combined with near-bit logging-while-drilling (LWD) tools to land the well. Because the pilot section is often drilled with water-based mud and penetrates through multiple layers of unstable shales and the reservoir, the hole condition normally deteriorates especially after extensive wireline logging runs, even after the cement plug has been set. In collaboration with other service providers such as cementing and wireline, the directional service provider revisits the sidetracking procedures to improve the sidetrack operation and reduce overall well construction time. Combining extensive data otherwise kept within each service provider's domain, the directional service provider analyzes the hole condition specific to each pilot section using formation evaluation data, wireline caliper logs, and pilot section drilling mechanics data to determine the sidetrack depth, drilling parameters, cement plug type, and the optimized RSS and BHA to perform the sidetrack efficiently. This detailed sidetracking procedure is then shared to all concerned parties, including to clients at the wellsite and in the office, and other service providers for discussion to align all objectives and ensure the sidetracking operation will be efficient. In 2018, the operator implemented the sidetracking procedures on 9 wells and achieved 100% success for drilling sidetrack from shoe-to-shoe in a single run. The detailed procedures mitigated the risks of using an RSS and subsequently eliminated the need to run a PDM to initiate the sidetracks. Comparative to sidetracks performed by the PDM, the sidetracking procedure using the RSS BHA managed to reduce drilling time on average of 1 day per well. The RSS BHAs also improved the hole condition for the subsequent activities of the well construction cycle, leading to less casing running issues and improved torque and drag for subsequent sections.