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Abstract The oilfield industry is facing more challenges as wells have become more complex. Companies are designing casing programs that utilize larger casing sizes and setting them deeper than ever before. For cased hole sidetracking projects, this means sidetracks with increasing levels of difficulty such as thicker casing walls, double casing exits, and extended ratholes. These new challenges also represent issues involving premature cutting structure damage, ringouts, coreouts, twistoff, and undergauge windows and ratholes that require unplanned or additional runs—both of which result in nonproductive time to the operator. The ability to analyze and predict the performance of milling tools is critical, and reliability performance curves provide value to the remedial operation planning phase of the sidetrack project. These curves can also be used as a decision-making tool while on a job. These are the first known reliability and performance curves for sidetrack milling tools. The curves are built using 10 years of historical data, including mill type, size, and casing grade. The parameters were selected based on acceptable gauge criteria, among others. Up to six casing grades can be analyzed and compared for median hours of milling, average ROP, percentage of cutting structure wear, and milling tool reliability. These curves establish a baseline of performance for mills in their current and future designed state. Any future design changes can then be referenced against these curves to monitor improvement of the tools over time. Engineers may also utilize the curves to conduct operational risk assessments and estimate the performance of mills, especially in challenging environments such as hard formations or thick or double casing string applications. Educated decisions can then be made to prevent or reduce unexpected time loss. Reliability curves are being generated to improve planning for sidetracking operations as well as making informed decisions on when to pull a mill and replace with the backup. This helps to maintain a full-gauge window or rathole, avoiding tool failures, unplanned trips, and nonproductive time. This decision-making tool can save valuable rig time, which is increasingly important with larger spread rates and deeper wells. A real scenario was analyzed from a previous job and demonstrated that using the curves as a decisionmaking tool could have saved 30% of the actual downtime.
- Asia (0.47)
- North America > United States (0.28)
Novel Lubricant - Bridging Agent Combination Cures Differential Sticking Problems in High Pressured North Kuwait Wells
Al-Muhailan, M. S. (KOC) | Al-Foudari, Saud Jumah (KOC) | Debroy, Amalendu (KOC) | Rajagopalan, Arun (KOC) | AbouElkhair, M.. (Halliburton-Baroid) | McNaughton, P.. (Halliburton-Baroid)
Abstract Deep wells drilled into the Jurassic formations of North Kuwait pose a drilling challenge due to the existence of low pressure reservoirs separated by an extremely high pressure salt zone. Currently, the seven string casing design in these wells leaves no further option for zonal isolation. As a result, a wide range of pore pressures are encountered while drilling these formations. Depleted zones/reservoirs in these wells suffered multiple instances of differentially stuck pipe and side tracks. The end result has been a significant loss of expensive rig days. These sections are drilled using oil based mud (OBM) with a high oil/water ratio and mud densities ranging from 10 to 17 ppg. To prevent a reoccurrence of the differential sticking problems, extensive laboratory work was undertaken to determine how to negate the effects of high differential sticking force while drilling depleted zones. Laboratory tests and fracture modelling based on historical data were carried out to develop a suitable fluid formulation to address these challenges. This work indicated that a novel combination of glycolic polymer lubricant and sized marble bridging agent provided the optimum combination of lubricity and filtration control to minimize differential sticking tendency. A fluid formulation based on the laboratory results was utilized to drill subsequent wells in this field. The depleted intervals were drilled using a similar OBM treated with a combination of unique lubricant and sized marble bridging agent to reduce differential pressure transmission across the depleted zones. The intervals were drilled and logged without the occurrence of any problems of differential sticking. The troublesome sections were completed incident free resulting in huge savings in cost and rig time. This paper describes the historical challenges in this field and present case studies demonstrating how the solution was successfully implemented in the field.
- South America > Falkland Islands > South Atlantic Ocean > F3 Sands Formation (0.99)
- South America > Falkland Islands > South Atlantic Ocean > F2 Formation (0.99)
- Africa > Nigeria > Bayelsa > Niger Delta > Niger Delta Basin > F1 Formation (0.99)
- (2 more...)