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.
In close collaboration with the operator, third party suppliers and the integrated drilling service contractor the first Integrated Drilling Project in Kuwait started in March 2016. The project is being treated as a pilot to assess the value integration can bring to the operator by providing the expertise, new technology and processes for managing drilling risks and improving performance. The project scope includes the provision of all services, engineering and supervision for the well construction process under a lump sum model. The project had an original target start date of June 2016, a year after the contract award. However, in the current challenging oil and gas industry environment, coupled with the operator's ambitious plans to increase oil production, the requirement for drilling more wells to provide the necessary increase in oil output meant that an early start would help in accelerating oil production from the Sabriyah and Raudhatain fields. From the onset, the target was set for exceeding client expectations. It required a very detailed planning approach to avoid potential short-sighted risks that could lead to costly delays. This paper describes the success case of advanced planning of a fully integrated approach. Three primary challenges were identified for the early startup, i.e. drilling rigs readiness, personnel and processes. For the drilling rigs readiness, the main issue was the utilisation of an interim rig requiring major equipment overhaul, including engines, top drive, mud pumps and drawwork, followed by an audit and certification. A specialised and dedicated team was mobilized to manage this operation successfully, and better support the rig contractor, including a rig contractor manager, rig managers, electricians and mechanics. Key project team members were brought in ahead of time, through careful selection to ensure the right competencies, according to the technical complexities and contract requirements. The team in place focused on implementing processes to accommodate operational and engineering optimizations as well as new technologies which could be applied from the first well, in order to improve well contruction cycle and deliver more wells in shorter time to the operator. This required collaboration from both teams including the integrated drilling service contractor and the operator. For ensuring the project readiness, a thorough process assessment was followed for each of the established milestones in the schedule. These assessments covered different functional areas including HSE, engineering, drilling services, third party providers, resources allocation and technology review including cost versus benefit analysis. In result, close collaboration and hard work of integrated team including operator, third party suppliers and integrated drilling service contractor, enabled successful project start-up. The drilling operations commenced three months ahead of plan, exceeding expectations of all project stakeholders.
Sidetracking a preexisting drilled and cased wellbore poses numerous challenges. When sidetracking in an openhole environment, additional verifications of hole conditions are needed, which contribute additional unique challenges. In this type of wellbore, the operators must plan by selecting the sidetracking depth and then ensure that all the objectives are met from a well authorization for expenditure standpoint and geological target perspective. The quality of the openhole window or rathole is of immense concern to operators because this quality ensures that the bottomhole assemblies (BHAs) will pass through the rathole without difficulty. The openhole gauge must be confirmed because it can pose additional risks that might lead to costly multiple trips into the well to ensure that the rathole is in good condition. This paper presents a unique case study in which the operator, Kuwait Oil Company (KOC), was faced with the possibility of geological losses at the kickoff in the wellbore while attempting to sidetrack an existing wellbore. The operator contacted an oilfield services company and requested a unique technical solution to precisely sidetrack the wellbore in the difficult formation containing fractured dolomites, which are known to cause severe to complete losses. While drilling the 12.25-in. section, the BHA became stuck in the fractured dolomitic limestone formation. In this section, the operator had previously experienced severe to complete losses. Because fishing attempts to free the stuck BHA were not successful, the operator decided to sidetrack the wellbore in the open hole using an openhole whipstock. A casedhole sidetrack option was ruled out because reactive swelling shales with producing sands were located above the sidetrack depth; therefore, combining these zones was not practical because of the low-mud-weight limit required for drilling the fractured dolomite below the target depth. In addition, because only 70 ft of open hole existed between the 13.375-in. casing shoe and the stuck BHA in the hole, sidetracking with a cement plug was nearly impossible. The openhole wellbore was logged with a caliper to confirm the wellbore gauge. Prejob planning consisted of understanding the compressive rock strength from the offset wells to identify the lithological challenges unique to this application. A hazard analysis risk-control method was adopted to identify the risks and apply appropriate mitigation measures. An operating parameters plan was formulated by the engineering team and discussed with the operator and service company personnel and followed throughout the job. The wellbore was successfully sidetracked in the 12.25-in. section in a single run using an openhole whipstock, avoiding the loss zone, and resulting in additional cost savings to the operator. The condition of the sidetracked rathole enabled smooth passage of the directional BHA to meet the directional objectives. Furthermore, the openhole whipstock operation eliminated the need for multiple cement plugs in the sidetrack (in view of severe loss zones below) as well as the time required for drilling with a dedicated motor BHA for openhole sidetracking operation, saving the operator a minimum of 6 days of rig time. This operation was the first successful 12.25-in. openhole sidetrack operation in the Middle East, Asia-Pacific, and sub-Sahara Africa regions. As a result of this successful operation, the operator is proactively recommending the new solution across the entire KOC organization for wells with similar scenarios. By applying this unique and reliable openhole whipstock technical solution, the drilling team was able to deliver a successful well based on the original casing plan without any need for further sidetracks or changes to the wellbore casing design.
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