The Wisting Field is located offshore in the Barents Sea north of Norway. The field development requires drilling and completion of horizontal wells in a narrow pressure window, which is challenging for conventional technology. The Reelwell Drilling Method (RDM) provides a solution for managed pressure drilling (MPD) to mitigate these challenges. Based on the use of dual-channel drillpipe, RDM enables the pressure gradient in the openhole section to be held constant and nearly independent of the drilling fluid flow rate. RDM provides low-energy drilling, i.e., efficient drilling and hole cleaning when using low flow and low-drillstring rotation speed. This allows drilling of horizontal sections within a small pressure window and limits drillstring fatigue in high-dogleg applications. In order to start qualification of RDM for the Wisting Field, a horizontal trial well was drilled in fall 2018 at the Ullrigg Drilling and Well Test Centre, located at the NORCE Norwegian Research Centre in Stavanger, Norway. The goal for this trial well was to prove the dual-channel drillpipe capability to perform low-energy drilling, i.e., low-rotary speed, low flow, and stable downhole pressure gradient. The trial well had a challenging geometry with up to 14°/30-m build rate, as required for the field. The 9½-in. horizontal section was drilled in order to check the performance of the RDM and start the qualification of the RDM for the Wisting Field. The trial well was drilled with a low-flow motor, i.e., with flow rates around 700 lpm. The string rotation speed was held lower than 5 rpm to limit drillstring fatigue in the high-dogleg section of the well. Efficient drilling and hole cleaning of the 9½-in. horizontal hole section was demonstrated. The results from the trial confirm the predicted performance for the RDM. The results indicate that RDM can keep well pressure gradient within the required window and mitigate the drilling challenges for the Wisting Field. The RDM architecture with return flow in the inner string represents a major advantage to avoid cuttings build up in the well, challenges with laminar return flow, formation wash-outs, mechanical down hole dynamics and ECD control by low energy drilling.

The Culzean field combines both UHPHT reservoir conditions and an unusually narrow drilling window, at the top of the main reservoir, where reservoir pressure lies on a regional ‘broken seal’ rock strength line. This drove a need to find an improved well architecture, to allow production wells to be drilled close enough to the reservoir crest to maximize gas production volumes. The solution: to develop heavy, ultra-high strength, sour service tubulars and use these in a well layout more typical of Deep Water designs than North Sea HPHT wells. Instead of setting a full production casing string, before drilling the target reservoir, a short production casing liner is hung from the fully rated sour service intermediate string, and tied back after the reservoir section has been drilled and a production liner run. This greatly reduces drilling circulating pressure losses in the reservoir section, allowing crestal targets, whilst providing very robust intermediate and production casing strings for long term well integrity. The reduction in ECD combined with the use of MPD technology, enables the drilling of this complex reservoir, in a safe and efficient manner.

Abstract This paper introduces a method for selecting the best sensor layout when using wired pipe for drilling operations. The introduction of wired pipe in drilling operations increases the data rate significantly compared to standard telemetry systems. Various sensors systems are available, measuring parameters such as drillstring vibration, drillstring torque, downhole fluid temperature and downhole annulus pressure. Also available are measurements from various logging tools placed as a part of the bottomhole assembly. The data from the sensors can contain important information that can be used for preventing various operational problems, such as high vibrations, insuffcient hole cleaning, kick incidents, and loss of circulation. The method described in this paper can be used for designing a sensor layout for a wired pipe drillstring. The method analyzes data available from the sensors to yield the information required to detect operational problems. The paper presents two different cases where the method is applied, one from a kick incident and the other from a loss of circulation incident. The results show that by optimizing the sensor layout for a wired pipe drillstring, cost efficient performance can be ensured with regards to potential drilling problems. Introduction During drilling it is important to avoid non-productive time. To avoid such situations, data can be gathered and used for extracting information about the well and the formation. Various types of sensors are being used during drilling operations, measuring different physical properties of the formation and the well. One of the challenges during drilling operation has been to transfer data from downhole sensors to surface. The wired pipe drillstring has been used to provide large amounts of drilling data during the operation. In a wired pipe drillstring, a data cable is integrated into each pipe joint and has the possibility of transferring data from the sensors at the drill bit. In addition, data can also be transmitted from sensors mounted along the drillstring. The data cable gives the possibility of sending large amount of data from the sensors along the drillstring while the drilling process is in progress 1,2. Various methods for automatic analyzing, presenting and evaluating the data has been examined, to be able to transform the data into information 3. A further evaluation of existing sensors and suggestion of new sensors and their placement should be performed. In production wells, an evaluation method for sensor selection and sensor placement with regards to predicting reservoir production rates has been developed 4,5. The current paper focus on ranking the usefulness of various sensors when performing a drilling operation. The sensors selected in this paper are sensors that gives information about the fluid flow in the well, and the focus has been on pressure sensors and flow sensors. The temperature gradient between the well and the reservoir fluids are not included in the model, so the importance of temperature sensors should be further examined in a future study. The paper is divided into five sections. In the next section a description of the theory regarding modelling and ranking methods is presented. Section three briefly presents two cases where the ranking method is applied. In section four the main results using the method are presented and discussed, and conclusions are given in section five.