The challenging environment in the Kvitebjørn field offshore Norway comprises high-temperature wells, long drilling hours, low rate of penetration (ROP), managed pressure drilling (MPD), and mud additive requirements, all of which are very detrimental for operations and reliability of the positive displacement motor (PDM) power section. In fact, until now, no one has successfully drilled the 5 ¾-in. section in a single run due primarily to motor failures such as elastomer chunking and debonding. This paper presents the steps used for optimizing the selection of a PDM section to achieve a single-run drilling operation with improved ROP. The method includes understanding the drilling environment, type of wells, rig capabilities, formations, temperatures, MPD, and drilling fluid requirements. Furthermore, the usual motor and bottomhole assembly requirements must be evaluated and the mud compatibility with the elastomer must be scrutinized. All of these variables were then input into a modeling engineering workflow to simulate and analyze the power output, the elastomer fatigue life, the hysteresis heating, and the debonding stress to select the best possible PDM candidate for the drilling job. A new long-life elastomer and the drilling parameters recommended by the mud motor modeling resulted in drilling this section in a single run for the first time in the field. Simultaneously, it was possible to drill to the deepest total depth without any need to set the section total depth shallower, as occurred in previous wells due to motor failures. The motor drilled through a very thick cemented sandstone stringer with no stall incidents. This motor set new records for drilling the 5 ¾-in. section with a total run length 60% longer than the previous longest run and a total pumping time 67% greater than the previous record. The combined new technologies of the modeling and the new long-life elastomer were applied for the first time in the anticipated challenging drilling conditions. The successful results demonstrated that with thorough analysis and proper planning, one can achieve a step change in performance and reliability without additional costs. The scope of the operation is even broader than the mud motor application.

The objective of this case study is to share essential learnings from the planning and execution of the first drilling and completion campaign in the Valemon field throughout the period of 2012-2017 with a total delivery of 17 wells. The case study will give an overview of the Valemon field, geology of the area and well design. The development of well trajectory became longer and more challenging as the geology targets moved farther away from the platform. Several major challenges and learnings were experienced during execution such as enabling one run strategy in 17-1/2" section, updating well path strategy to improve borehole stability, managing overburden gas responses in 12-1/4" section, and section target depth strategy for 12-1/4" section. Continuous learnings from sessions such as Improve Well on Paper (IWOP), Drill Well on Paper (DWOP), Subsurface Action Review (SAR), Subsurface After-Action Review (SAAR), operational procedures after action review, experience reports, and post well meetings enabled the project to reduce the time and cost per well. It took 160, 111, and 166 days respectively to complete the first three wells. The last well was delivered in 62 days. By the end of the campaign in November 2017, the Valemon project delivered four (4) extra wells compared to the original plan of thirteen (13) wells, while spending 500 million NOK-2017 (Norwegian Kroner with 2017 currency) or 60 million USD-2017 (United States Dollar with 2017 currency) less than the planned budget. Moreover, the entire drilling campaign was completed without any well control incidents.

The main objective of this paper is to share the experience of the first Dual reamer bottom hole assembly (BHA) design implemented off-shore Norway, Gullfaks field, 17 ½ × 20-inch section. It presents the drilling challenges, innovative bottom hole assembly and the first world wide application for the Electro-magnetic receiver sub fully integrated with rotary steerable system (RSS) Hole enlargement while drilling (HEWD) became a well-known application, and they are widely used to support several well intervention objectives like; i) Accommodating un-common casing design. ii) Reduce operational risk such as high equivalent circulating density (ECD). iii) Optimized casing and completion programs. There are two main types on hole enlargement tools, based on activation mechanism: ball-drop using a ball to Activate/De-activate the reamer, and hydraulic on demand triggered by changing flow rate on a predefined specific range, so called ‘Indexing’ for Activation/De-activation of the reamer. Both carrying a common implicit risks and limitations, where reamers have to be positioned above logging while drilling tools (LWD) so that the enlarged hole does not impair the quality of the formation evaluation measurements, or compromise the bottom hole assembly stabilization. This results in a rat-hole of 40-50 meters at the section target depth (TD), consequently challenges the casing running, casing cementing job, and drilling next sections with potential risk of cement pack-off around bottom hole assembly. Today in the industry, these challenges are usually addressed by an extra dedicated run for opening the rat-hole. Collaborative efforts between operator in the North-sea and a Service Company to address the risk and limitations associated to the hole enlargement while drilling design. Dual Reamer System developed to reduce the rat-hole length to minimum instead of 40-50 meters, and to eliminate the extra dedicated run for opeing the rat-hole. The innovative approach planned to drill to section target depth (TD) using upper ball drop reamer, tool positioned 45 meters behind the bit for Hole Enlargement While Drilling, then pull back to position the bit at rat hole shoulder, de-activate upper reamer (ball drop system), and activate the lower hydraulic on demand reamer to eliminate the rat-hole. A Gyro while drilling integrated into the BHA along with 9-in world first electro-magnetic receiver sub mounted on the top of the hydraulic on demand reamer. Providing a full integration, and securing a real time communication with the RSS in a critical and challenging Anti-collision situation. The unprecedented approach successfully implemented on Gullfaks field, 17 ½ × 20-inch section drilled to target depth (TD) in one run, with all objectives met on directional control in tight Anti-collision scenario, and measurements and logging while drilling. The Dual reamer BHA along with the Electro-magnetic receiver sub proven efficient steering capability and reliability, which led to significant improvement in the drilling, casing running and cementing operations

This case study aims to share the experience and improve the understanding of downhole shock and vibration and demonstrate how it can be prevented using thorough offset analysis, an advanced bit design, downhole mechanics module, and detailed drilling roadmap. The new approach delivered a step change in the performance of the 17 ½-in. section in Valemon field, in the Norwegian sector of the North Sea. Employing a one-run strategy through this extremely demanding section could eliminate the need for a dedicated motor run to withstand high shocks through the sandy interval with interbedded limestone and cemented sand layers. Using a point-the-bit bottomhole assembly (BHA) with a detailed drilling roadmap for every group of formations secured smooth drilling, pull out, and running of the intermediate 14-in. × 13 3/8 in. casing to provide integrity to drill 12 1/4-in. section. An advanced bit design balanced drilling with low aggressiveness through sand without compromising the performance through the interbedded limestone stringers and claystone. The conical-shaped cutter placed behind the main PDC conventional cutters successfully controlled the depth of cut through the sandy intervals and mitigated the downhole shocks. A detailed drilling roadmap was developed to define formation-specific drilling parameters to mitigate the shock-related failures on similar lithology. A downhole drilling mechanics module was used to provide real-time axial, lateral, and torsional shock and vibration data, which enabled adjustment of surface drilling parameters accordingly.

In this case study, we present the use of a new look-ahead resistivity technology to solve a challenge on the Valemon field where the top of the reservoir could not be mapped from surface seismic. The objective was to extend the overburden section deep enough to secure sufficient formation strength at the casing shoe while eliminating the risk of accidental drilling into the reservoir below. The application of the new technology secured standard casing design, and eliminated the extra time and costs associated with implementation of the managed pressure drilling technique. The target was to extend the 12 ¼-in overburden section 10-15m TVD into the Viking Group, as this formation generally provides sufficient formation strength for the 9 7/8-in casing shoe to enable conventional drilling of the following reservoir section. As there was a risk that the Viking Group could be absent or very thin in this area of the Valemon field, the look ahead measurement was used to monitor the formations ahead of the bit while drilling. Detection of higher resistivity ahead of the bit indicating an approaching reservoir would enable stopping prior to drilling into it. No reservoir response was detected ahead of the bit, and this enabled a safe extension of the 12 ¼-in section into the Viking Group as per the objective.