Drilling the 16-in. section in Umm Gudair field in western Kuwait faces a lot of challenges while drilling. Challenges include drilling through severe loss conditions, destabilized shale, and deteriorating hole conditions. These conditions can result in hole collapse or lost in hole of the drill string that requires sidetracking. The objective of project presented in this paper was to develop an engineered solution to drill through the difficult zones, lessen nonproductive time, and reduce the total well cost. The solution proposed was to use casing-while-drilling technology with a drillable bit and drill through the fractured dolomitic limestone and sandstone formation while simultaneously setting casing. The drillable casing-while-drilling bit was specifically designed and engineered to conform to the formations in the field. The drillable casing-while-drilling bit is manufactured with a material that can be drilled out with either conventional roller cone or fixed cutter bits. A plastering process was used, which smears the cuttings generated by drilling against the borehole wall, seals the pores or fractures in the formation, and helps reduce fluid losses while maintaining well integrity. The successful implementation of 16 × 13.375-in. casing-while-drilling job in Umm Gudair field reduced well delivery time for the operator and saved 17 rig days with cost savings of 450,000 US Dollars considering rig rate only. The section was drilled successfully while encountering total mud losses through fractured dolomitic limestone and sandstone formations. Preventing the risk of losing the bottomhole assembly in the hole and alleviating the use of multiple cement plugs saved additional cost for loss-cure plugs to heal the loss-prone formations. After reaching the target depth, cementing, pressure testing of the casing were carried out successfully. Lesson learnt from the first job were applied in the subsequent job completing the section with faster ROP with substantial savings to operator. For both the jobs, drillout of the drillable casing-while-drilling bit using a fixed cutter bit and Rotary Steerable bottom-hole assembly were performed successfully, the drillout bit continued drilling to section TD in one run. With the successful implementation and the savings obtained by using this casing-while-drilling technology in the West Kuwait field, there is the potential for substantial annual cost savings, aiding the operator deliver wells in less time, and eventually increase production by increasing the number of wells drilled per year.

Reduced land slots availability for drilling of new wells, operator's focus to increase production, aim to reduce effective cost per barrel and to minimize the environmental footprint, worldwide drilling contractors/operators are looking for various solutions available to address these concerns. Drilling multilateral wells is one of the solutions to these concerns. This paper presents the process and steps followed in planning and decision making for drilling a multilateral well in one of the North field in Kuwait, which includes Identification of filed and understanding formation, Categories of multilateral wells and selection of level and types of multilateral well, Pre requisition of data for level 1 multilateral well, Selection of well slot and reviewing additional tools/service requirement, Selection of well trajectories for multilateral well, Selection of open hole junction point, Selection of section TDs, Review of directional BHA & its suitability for open hole side track, Well control scenarios, Well stimulation plans, Review of Coil tubing (CTU) operation for stimulation and tools requirement, Contingencies plan for reservoir section, Cost saving, higher production, environmental footprint, well completion days.

Drilling the 16" hole section through mostly carbonates in southern Kuwait presents several distinctive challenges. Interbedded formations with vastly different compressive strengths that vary between 5-30 Kpsi and a significant amount of blind drilling can result in twist-off and lost-in-hole situations. The most common tungsten carbide insert (TCI) rollercone bit failures mechanisms are impact induced cutting structure damage, hydraulic inefficiency issues and bearing failure caused by high weight-on-bit (WOB) through the hard Dammam to Ahmadi carbonate sections.To solve the challenges the operator's drilling team, working in conjunction with the bit supplier, launched a performance improvement initiative. The carbonate application was analyzed using finite element analysis (FEA) based dynamic simulation program to fully understand how to stabilize the bit in different downhole conditions and improve hydraulic efficiency. Based on the computer analysis and field run data, engineers conceived a new stable bit design. The technology platform includes improved hydraulics and a specialized cutter structure configuration with tougher insert carbide grades to mitigate impact damage. A high-aspect ratio seal employs two dynamic sealing surfaces (ID, OD) that reduces frictional heat and minimizes wear to improve bearing reliability.The new rollercone bit was run with an optimized drilling plan with outstanding results establishing a performance step change in southern Kuwait's carbonate applications. The bit recently set a new 16" world cumulative TCI footage record of 12,656ft drilling three wells shoe to total depth (TD) and 531ft of a fourth well. The bit amassed a total 446 hours of onbottom drilling time turning 2.4 million revolutions without a seal failure. The bit saved the operator 4.5 days of rig time plus bit spend. The new technology has enabled the operator to drill long footage intervals or multiple wells using a single bit with good penetration rates (ROP). The authors will discuss the formation challenges, application analysis and resulting performance improvement.

Kuwait Oil Company embarked on an ambitious project to look for gaseous Hydrocarbons in a hitherto un--proven formation in the North Kuwait Field. As the target formation was extremely depleted and usually was drilled through under--total--loss conditions, these wells were designed to be Under--Balanced--Drilling (UBD) wells.The design conditions for an Under--balance or drawdown of 10% below formation pressure of the target zone called for Nitrified water as the fluid medium. Design simulations showed a normal Nitrogen pumping rate of around 1100 scfm for maintaining the UB conditions. Further testing of the target formation called for a huge drawdown of a maximum of 30%. This led to extreme conditions of pumping Nitrogen at the rate of 2000 scfm. The normal operating conditions with membrane NPU resulted in 5% Oxygen being pumped in with Nitrogen. This resulted in a highly corrosive environment under Bottom--hole conditions, especially when we started producing highly saline formation water. The above conditions led to very severe corrosion of our Drill string and UBD Coring equipment, creating a potential hazard of losing our whole string.Conventional corrosion inhibition completely failed to arrest the corrosion of the string. This led to intensive study and debates within the team to find a solution to the problem and quickly too. A multi--pronged solution comprising of controlling pH, usage of Phospate Ester Inhibitor formulation, filming amine and monitoring through usage of Corrosion coupon rings in the drill string led to a dramatic improvement of the corrosion damage.Corrosion hazards in UBD wells are a reality and a heady--mix of ideal conditions for corrosions could mean disaster. Conventional Corrosion programs usually fall short of dealing with the severe corrosion existing down-hole. Special operations such as Underbalanced Coring could fail dramatically before achieving objectives. A multi--pronged approach needs to be designed and the severity of the problem understood before embarking on such ambitious projects. The authors are going to present a strategy for putting the best foot forward when dealing with such issues. Being forewarned will always mean being forearmed.

Promotion of horizontal well drilling started with inflow control device (ICD) completion to boost the hydrocarbon production as per the KOC 2030 strategy. Drilling these wells revealed many technical issues leading to stuck pipe due to improper hole cleaning. The rate of penetration (ROP) in the buildup and lateral sections was erratic. Drilling a pilot hole and performing pipe-conveyed logging runs were the main factors contributing to excess rig time. It was observed that drain hole cleaning methods and drilling time optimization needed to be improved. These factors increased rig time by about 40 while drilling many horizontal wells in the North Kuwait (NK) horizontal operation, adding significant costs to the well budget. While drilling these horizontal wells, well design was optimized and the drilling team applied the optimized design that increased hole-cleaning effectively, improved ROP and reduced the logging time. The 6⅛-in. and 8½-in. motorized rotary steer-able systems (RSS) and bottomhole assembly (BHA) systems ran for the first time in Kuwait, drilling 8½-in. build section from Mutriba to the Upper Burgan top formation and 6⅛-in. section in Mauddud carbonates has dynamically avoided down-hole tool failures, doubled the average ROP, and reduced non-productive time (NPT). The pilot hole section was designed and drilled in two phases. In the first section a gamma ray tool identified the formation tops. The second section (zone of formation interest) was then drilled using an 8½-in. tool with a triple-combo RSS BHA. This approach reduced the extensive wireline or tough logging condition (TLC) runs and increased ROP by slimming down the borehole size. The hole-cleaning method was modified by combining pumpout techniques with heavy-weighted pills (MW+2 ppg). This technique was used in horizontal wells, resulting in reduced drilling time and well cost.