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Abstract Following the significant reservoir depletion on Elgin / Franklin fields since 2007, drilling infill wells was considered to not only be high cost but also carry a high probability of failure to reach the well objective. The recent campaign on the Elgin field, one of the most heavily depleted reservoirs worldwide, demonstrated that infill drilling can be achieved safely while improving performance. Drilling of HPHT infill wells on the Elgin field faced increasing challenges arising from the reduction of reservoir pressure that changed the stresses in the formations above and influenced the overall pressure regime. This stress reorganization in the overburden has affected the fracture network in these formations resulting in reduction in Fracture Initiation Pressure (FIP) and increase of gas levels. Challenges were faced during the drilling of three wells in the 2015-2017 campaign. Loss events in Chalk formations in the intermediate sections significantly decreased the already Narrow Mud Weight Window (NMWW). A strategy to define and validate the minimum required MWW in 12-1/2" and 8-1/2" sections was developed following a complex subsurface well control event. Managed Pressure Drilling (MPD) technique was extensively used to safely manage gas levels and assess pore pressure. Reservoir entry with more than 850 bar of overbalance remains the main challenge in infill drilling. A total loss event during first reservoir entry in the latest campaign confirmed the limitations of wellbore strengthening mud and stress caging materials available today. Lessons learned from each well in this campaign were implemented to address these challenges and improve performance. This paper describes the Elgin HP/HT infill drilling experience and the specific techniques and practices that were developed to address these challenges and improve performance. The importance of Equivalent Circulating Density (ECD) management with very narrow MWW, successful high gas level management with MPD and depleted reservoir entry, shows that even in a highly complex environment, drilling performance can be improved allowing for further economical development drilling. The successful and safe delivery of the Elgin 2015-2017 infill drilling campaign demonstrates this at a time the industry moves toward unlocking the reserves of more challenging HPHT fields.
Epps, Steve (Lavaca River Operating Company) | Pellegrini, Thomas (Lavaca River Operating Company) | Valecillos, Juan C. (Weatherford International Ltd.) | Craig, Hunter (Weatherford International Ltd.) | Arnone, Maurizio (Weatherford International Ltd.)
Abstract Multiple operators had attempted to conventionally drill wells in an area of south Texas targeting an over pressurized sand. A majority of them were unsuccessful showing a history of lost time events and poor well results related to kicks and losses. Information suggests little was known about the pore and fracture pressure gradients, and that uncertainties regarding real stratigraphic distribution were present, resulting in improper casing points and mud trends not in accordance with actual wells requirements. For these reasons, one operator decided to implement Managed Pressure Drilling (MPD) technology in order to safely and efficiently drill a well to the pay zone. The scope of the operation was a re-entry sidetrack on a vertical well that originally encountered well control and multiple mud losses events. The first interval was an 8-1/2 inch intermediate section to be cased with a 7 inch liner. The liner shoe was to be set approximately 80 feet above the over pressurized target sand. The second interval was a 6-1/8 inch production section targeting the well pay zone, to be cased with a 4-1/2 inch production casing. Both intervals were considered critical, the first one having depleted zones interbedded with gas bearing formations with a final depth immediate to abnormal gas pressures, and the second demanding accurate ECD management to avoid well control events, losses and formation damage, this of cardinal interest for the operator. The implementation of MPD enabled both intervals to be drilled to the planned target in a constant bottom hole pressure (CBHP) state safely and efficiently. The well was drilled near balanced to improve drilling efficiency and increase the ability to identify pore pressures. The annular pressure profile was adjusted instantly as the well dictated by means of MPD surface equipment avoiding kicks and losses. Continuous evaluation and monitoring of well behavior in real time allowed for pore pressure predictions, which were later used to plan proper kill mud weights, tripping/stripping procedures, and managed pressure cementing operations. Implementing MPD techniques and technology proved successful in enhancing safety and drilling efficiency on a well with many uncertainties and potential hazards. This paper will describe the planning and execution of a successful drilling operation on a high potential oil/gas producer well using MPD techniques in an area where others were unsuccessful.
Abstract This paper presents the novel approach used in drilling, running liner and cementing a development well across multiple reservoir with high pore pressure heterogeneity that has historically caused drilling hazards like differential stuck pipe, losses, well control and slow rate of penetrations. Having depleted reservoirs and high-pressure reservoirs in the same hole section of well-A dictates that the mud weight must be higher than the higher reservoir pressure, which puts high differential pressure on the depleted reservoir and causes differential stuck pipe and losses. The uncertainty in determining the pore pressure adds another challenge as the mud weight must be higher than the expected pore pressure. Managed Pressure Drilling (MPD) addresses these challenges by enabling determining the pore pressure while drilling and adjusting the Equivalent Circulation Density (ECD) to be with the minimum overbalance. MPD allowed drilling the section with (12.0 ppg) mud weight instead of the conventional mud weight (15.7 ppg). This has reduced the differential pressure between the depleted formation and the other formations significantly and enhanced the rate of penetration while balancing the well. It also proved that verifying the well's prognosis for pressure is essential in avoiding drilling hazards. Constant Bottom Hole Pressure (CBHP) mode of MPD was used to maintain the same ECD while drilling and connection to avoid well influx during pumps off events by compensating the annular friction pressure loss by surface back pressure. MPD was utilized too in running the 7″ liner and cementing it as a guarantee if the mud weight was too low to stabilize the well. The operation was carried out without safety or quality issue. The MPD system performance was with zero nonproductive time and the hole section was drilled shoe-to-shoe without any change the Rotating Control Device (RCD). This application showed an alternative preventive solution to differentially stuck pipe instead of the reactive one. The approach explained in this paper is the first of its kind in ADNOC Onshore field. It involved altering the mud weight program strategically for more adaptive approach in dealing with drilling hazards like differential stuck pipe, losses and well control. The scheme involving MPD for running liner and cementing is the first ever in United Arab Emirates.
Abstract The deep basin of British Columbia, Canada contains the Montney and Doig plays, which are categorized as tight gas sands. Both are considered major unconventional gas plays containing vast quantities of gas in the west and oil in the coarser eastern facies. The formations have high initial formation pressure which promotes production, however during drilling causing drilling challenges. It is especially difficult when drilling through the abnormally pressured Doig transit zone. This is further complicated when a trip is required for the bit as the swabbing effect, if not properly managed, can easily escalade into a well control event. Due to the overpressured and geologically fractured formations, it is very difficult to trip the drill string out of the well safely without using specialized techniques. MPT is one such method that can be utilized in these scenarios. Managed Pressure Tripping allows the driller to control bottomhole pressure (BHP) in different types of abnormally pressured zones, and simultaneously eliminating the swabbing effects by holding surface back pressure (SBP) with the managed pressure drilling (MPD) system. Applying MPT techniques on subnormal and overpressured formations results in safe and cost effective drilling operations. This paper presents a case study where advanced Managed Pressure Tripping (MPT) technology was successfully applied in the Altares field in British Columbia, Canada, to mitigate well control challenges associated with swabbing. The study elaborates on recommended operational procedures, engineering calculations, equipment set up and process flow diagrams along with the analyzed graphical data.
This paper will discuss the Managed Pressure Directional Drilling fit-for-purpose solution deployed to meet the drilling challenges faced in 5 consecutive wells drilled in South Texas, USA. This innovative solution integrates a state-of-art Rotary Steerable System (RSS) with Managed Pressure Drilling (MPD) technology. Drilling hazards such as well control events, simultaneous kick-loss, and stuck pipe were mitigated, and an improved drilling performance with a reduction of NPT as compared to other directional drilling systems.
The solution requires the integration of two highly technical disciplines, MPD and Directional Drilling. Hence, a Joint Operating & Reporting Procedure (JORP) and a defined communication protocol are crucial for effective execution. The solution is based on a rigorous Drilling Engineering process, including detailed offset wells analysis to deliver a comprehensive risk assessment & mitigation plan in collaboration with the Operator to tackle drilling hazards without compromising the directional drilling requirements.
This paper will summarize the 5 wells operations, the drilling optimization results, and the lessons learned from an integrated services point of view in terms of deliverables that made the difference on this project and allowed the Operator to achieve their objectives. In particular, the effective communication protocol between the directional drilling services, MPD services, and rig contractors to ensure safe operational alignment.