Drilling to the targeted depth of a well can be a challenge, considering the problems that may arise in the form of wellbore instability, mud losses, and/or differential sticking. The objective was to successfully drill a first-time implementation of an Oil-Based Mud (OBM) system with 60:40 Oil-Water Ratio (OWR). The OBM system was maintained within the specified parameters in terms of mud weight, viscosity, and fluid loss. The addition of primary and secondary emulsifiers in the system enhanced electric stability (ES). Moreover, solid control equipment will be monitored continuously for immediate action if necessary. Contingency plan and a surplus of chemicals will be provided to ensure a smooth drilling and a swift movement of operations. A fluid system was designed after extensive laboratory tests to analyze the optimal approach to drill using the first-time application of 60:40 OWR mud. It reduces the use of Diesel consumption by 26% in total OBM formulation, lowers the percentage of Low Gravity Solids (LGS) compared to the 80:20 OWR mud, and decreases the impact on the environment. Furthermore, the OBM was then reused in consequent wells with the addition of emulsifiers to reduce the cost. This paper presents successful first-time applications of the 60:40 OWR fluid till the targeted lower Burgan formation, interbedded sandstone and shale formation. A complete laboratory analysis comparison between previous wells drilled and the current application indicates no difficulties were faced.

Drilling extended lateral sections to maximize reservoir exposure is key to optimizing field production and data recovery. However, it presents peculiar challenges not limited to hole-cleaning, wellbore stability, narrow drilling windows, and excessive torque and drag. Thus, customizing the fluid system to drill lateral sections requires information to understand the formation characteristics, including geomechanical data to determine the correct mud weight window, a precise selection of optimal fluid rheological properties, good inhibition, and lubricity, which are of foremost importance for extended-reach drilling (ERD) wells. The reservoir section of the well presented in this paper was previously drilled unsuccessfully twice, as the targeted zone was not reached. During the drilling phase, a large amount of non-productive time (NPT) was observed due to stuck pipe incidents, hole collapse, and then, hole cleaning issues were encountered while drilling. Another critical concern is the narrow mud weight window range, which causes the formation to break when Equivalent Circulating Density (ECD) increases beyond the pore pressure or fracture pressure of the formation. A new generation of High-Performance Non-Aqueous Based Mud (HPNBM) was engineered to drill these types of complicated, long horizontal intervals matching the drilling performance required to drill such sections and deliver a perfect gauge hole. This HPNBM provides high shear-thinning properties, an excellent low-end rheological profile, and rapid-set/easy break gels. This paper presents a successful well delivery of drilling the longest horizontal section in the country within a record amount of time. The previous attempts were carefully studied to identify the challenges associated during drilling and considered while designing this HPNBM. The high-performance non-aqueous based mud system proposed with stress caging technique was successful, economic, and drilled successfully with zero non-productive time (NPT) related to drilling fluids. Engineering software was utilized as hole cleaning is critical for drilling the horizontal sections to reach the targeted depth and run casing to the bottom. This paper presents the longest horizontal section (4,200 ft) to be drilled to the targeted depth as planned in Turkey. A comprehensive analysis that includes the planning phase, application, techniques, and performance of the mud system will be presented.

It is a challenge to drill a highly deviated or horizontal hole in high permeable formations. High differential pressures may lead to several problems like tight holes, wellbore instability, differential sticking and mud loss while drilling across these permeable or fractured formations. It was always preferred to drill these wells with Oil base muds which showed some success. While operators always prefer the standard solution, which is casing isolation for problematic sections, challenges have increased due to continuously drilling in depleted reservoirs which leads to considerable nonproductive time. The other solution to overcome such problematic sections was to re-design a fluid system that would target drilling through serious of highly permeable sand and shale formations. The fluid system would primarily address shale inhibition along with effective bridging, minimizing pore pressure transmission and wellbore strengthen with increased hoop stress in the wellbore. Software modelling and permeability plugging tests were performed to evaluate the fluid behavior under downhole conditions and to predict the characteristics of induced micro fractures based on rock mechanics. Porosity, permeability and induced micro fractures were considered to optimize the bridging mechanism. It was identified that normal bridging solutions involving calcium carbonates and graphite material were not enough to address the pore pressure transmission problem. It was essential to include a micronized sealing deformable polymer along with normal bridging material was effective in plugging pore throats and minimizing fluid invasion. The deformable polymer component is able to re-shape itself to fit a broad range of pore throat sizes which was previously unattainable with conventional bridging technology which was confirmed by particle plugging tests. A one well was identified to be drilled in highly depleted reservoir at an inclination of almost 45 degrees. The section involving the highly depleted and permeable sand involved drilling highly stressed shale formations which requires high mud weight for their stability. This was the first attempt on a high-angle well with development drilling operations in Kuwait and was performed to facilitate the successful drilling of the reservoir. Drilling and logging were successfully performed along with logging and LWD runs with no recordable differential sticking or losses incidents. This paper also presents 2 successful applications in the same field with the application of proper bridging and utilization of deformable sealing polymer to address drilling problems through highly depleted and permeable formations while managing over balance of 3500 psi across them.

This paper presents drilling and completion fluids design for drilling long lateral / horizontal wells in a North Kuwait field and its field application on well RA-AAA, RA-BBB, RA-CCC and RA-DDD. The offset wells were reviewed to identify the issues from drilling a challenging trajectory through troublesome reactive formations that showed serious wellbore stability issues and stuck pipe incidents.The customized drilling and completions fluids system was designed for different intervals, taking the following objectives in consideration:• Improved hole stability through stressed and reactive formations • Enhanced hole-cleaning efficiency at critical angles • Minimized risk of stuck pipe across depleted formations with high porosity and permeability • Minimized / no induced losses to formation by utilizing unique wellbore-strengthening technique • Minimal damage to reservoir section during drilling phase • Near-wellbore damage remediation during completion phase This paper describes the customized drilling and completions fluids performance as compared to offset wells. A comprehensive engineered approach addressed the challenges of drilling horizontal wells by using a revolutionary bridging technology to strengthen the wellbore and improve wellbore stability to reduce non-productive time (NPT) related to losses, stuck pipe, etc. This paper also describes the completions fluids design to minimize reservoir damage and utilize Mesophase technology to remediate near-wellbore damage and improve reservoir producibility. The lessons learned on these wells were incorporated in drilling subsequent wells to continue improve on performance.

Nowadays the global market demand for Heavy Oil is increasing and Kuwait Oil Company has a plan to increase the production of heavy oil, which is part of a long-term plan set out by parent group Kuwait Petroleum Corp. Drilling heavy oil wells needs a lot of efforts and expertise to be economically developed and produced. Gauged holes are the key for the production techniques used in this field, where cement channeling and perforation effectiveness are the main concern. To achieve this, a specific drilling fluid design was necessary. Laboratory tests and extensive research were initiated to customize the drilling fluid parameters and wellbore hydraulics necessary to achieve the objectives. The drilling fluid design goal was to provide enhanced inhibition for the clay and to provide good lubricity with a low friction coefficient to ensure smooth drilling and tripping operations in a gauged hole profile. This paper is describing the fluid behavior and hydraulics were designed in high profile to remain completely in laminar flow while drilling to minimize washout occurrence and maximize hole cleaning at low circulation rates (140 – 150 GPM) without the use of regular sweeps. The customized drilling parameters and practices, in addition to the knowledge gained from the laboratory testing phase, were transferred to the field. This resulted in field proven successes with more than 200 perfectly gauge holes being drilled. Case history from one well in Kuwait field is included in the paper.