While performing extended-reach drilling (ERD) offshore in the northern Caspian Sea, an operator required a new methodology to increase operating efficiency and reduce cost. With all modern downhole tools in place, it was necessary to use a system that allowed managing drilling parameters that directly affect rock failure at the bottom of a wellbore as well as bit performance. As a solution, a real-time drillbit optimization system was utilized to enhance the rate of penetration (ROP), decrease the bit wear while drilling, and ensure maximum length of runs.The main objective for implementing the drillbit optimization system was minimizing the human factor related to choosing operating parameters. The process started with offset well analysis, which helped identify weight on bit (WOB), revolutions per minute (RPM), flow rate, bit wear, and rock properties in relation to ROP. Based on performed analysis, the artificial neural network (ANN) was built for specific bits for every section of the well for the purpose of optimal WOB and RPM determination. Then, the recommended parameters were transmitted to the rig during execution, allowing the driller to make necessary changes on the fly to achieve optimized ROP. As a final step, based on post well analysis, the adjustment of the incoming parameters in the neural network was done for future improvement. The drillbit optimization system recommendations helped to increase ROP minimum by 6%.

Ensuring a quality cement job when cementing long sections of casing in high angle, extended reach wells is both critical and challenging due to the high risk of channeling and pressure related issues. Casing reciprocation is intended to mitigate against channeling; however, this technique is not widely used in ERD wells in the industry. This paper presents modeling, operational observations, and the results of 10¾-in production casing reciprocation during cement displacement on several extended-reach drilling (ERD) well projects. Accurate estimation of hydraulic lift force is one of the major challenges when planning casing reciprocation during cement displacement. The severity of the hydraulic lift force can cause the complete loss of slack-off weight when reciprocating on the down stroke, which is often perceived as the casing being "set" off-bottom. In order to accurately predict the hydraulic lift force and the associated hookload fluctuations, advanced modeling combining torque, drag, and hydraulics was developed. The model takes into account all of the key parameters such as slurries density and rheology, displacement rates, casing stroking speed, wellbore geometry, temperature and pressure effects, etc. In excess of 10 casing reciprocation jobs during cement displacement have been successfully modeled and executed to date. The first several wells were used for model calibration, and the modeled loads for the remaining wells showed consistent and accurate predictions when compared with the measured loads during the cement displacement. The casing strings that were modeled and subsequently reciprocated during cement displacement varied in setting depths from 2000 to 3100 m MD, with the top of cement lifted to the previous casing shoe. It was observed that the effective hookload when stroking the casing down can significantly decrease when the hydraulic lift force is high due to the combined action of surge and circulating pressure. Slack-off hookloads were monitored in real time to determine cementing friction factors. The friction factor data allowed for calibrating the model, which gave confidence to continue reciprocating throughout the entire displacement until bumping the plug. The casing reciprocation campaign has contributed to an increase in the quality of the cement bond throughout the casing string, thereby no longer requiring any remedial cement jobs, which was a common requirement on the previous wells. The technique and observations presented in this paper help close the gap that exists in the industry concerning the effect hydraulic lift force has on casing reciprocation operations. Understanding the effect is important in ERD wells, but can also be useful on other types of wells.

High torque, friction factors, and pick up weights were major challenges encountered by a major operator in Abu Dhabi while planning to drill challenging extended reach development (ERD) wells with complex 3D profiles. Well torque and drag simulations showed that planned depths were not reachable with water-based muds. This paper describes the implementation of a mechanical lubricant, which resulted in significant decrease of the friction factors and turned an ERD well from not drillable to drillable with water-based mud. After analyzing several possibilities, the solutions were narrowed down to two: use either a new generation mechanical lubricant or a reservoir non-aqueous fluid (NAF). The complexity was amplified by the necessity to re-design a filter-cake breaker for NAF, were this option to be selected, due to the type of completion. This second option would also create a substantial cost increase for the operator for products and rig time; therefore, the decision was made to introduce a mechanical lubricant. A comprehensive study and lab tests were conducted to ensure compatibility and stability of the lubricant with a planned mud type at downhole conditions. The results of this study were promising enough for the operator to introduce this lubricant, aiming a substantial reduction in torque and drag to enable drilling of the longest horizontal section in the history of the project. Before addition of the mechanical lubricant, drilling continued with a conventional type of lubricant, noticing an increasing tendency of torque and drag tracking the predicted trends. At a certain stage, drillstring buckling was observed and drillpipe started to reach their limits. To mitigate these impediments, the mechanical lubricant was introduced into the drilling fluid. After reaching the optimum concentration, the mechanical lubricant eliminated buckling and provided significant reduction in torque, pick-up, and slack-off friction factors, respectively by 27%, 52%, and 42%. These parameter improvements facilitated continued drilling the well to final depth without reaching the drillpipe limits. Additionally, the well and bottomhole assembly (BHA) designs allowed for significant margins in case of a stuck pipe event, and based on the new friction factors, the well could be extended by 3,000 ft without reaching the drillpipe limits. The impact of this exercise in future ERD wells is considerable. It will simplify well and completion designs, improve logistics by reducing the amount of chemical movements, facilitate drilling fluids selection, and optimize the well cost. The paper covers the gaps related to drilling complex ERD wells with water-based drilling fluids. It provides detailed methods and procedures covering the suitable application of the mechanical lubricant and the extensive laboratory tests done during the planning stage, as well as the field application and results. The proposed solution can be used during the well planning process in any other area of the world.

This manuscript describes the approach in the risk management developed and implemented while operating 21 drilling rigs on 13 fields simultaneously in the Middle East, which resulted in 40% reduction of non-productive time. Well construction process requires a lot of attention on different levels and from different sides to ensure trouble-free execution. The bigger the volume of work, the higher the chance of a costly mistake. The risk management process was split in several steps, where different levels and divisions are involved. The Planning stage starts at engineering level and associated risk review goes to a level of Division Supervisor for every well, when special tools were developed to focus on potential high impact events. The Execution stage was covered by a set of Critical Activity reviews and Standard operation procedures, focusing on operations with highest risks or highest benefits. Further at the Evaluation stage every well was analyzed following the developed workflow, and further all obtained knowledge shared with every team member via custom designed dashboards. Shortly after initial steps were taken under the new risk management approach, one of main KPI – non-productive time (NPT) – started to decrease and dropped by 5% within one quarter. Further tuning of the process allowed to decrease NPT by over 40% with continuous positive trend. One of the main contributors is the re-focusing on the prevention measures during planning stage, which avoid non-conformance events with high impact. Simultaneously the approach unified the practices of different divisions and remove misalignment on most of the technical issues and questions. Additionally, it decreased the workload of the key field personnel, as reduced NPT gives more time to focus on continuous rig performance improvement.

In the Middle East many of the matured fields have fractured or vugular formations where the drilling is continued without return to a surface. This situation has been commonly interpreted as lack of hole cleaning and high risk of stuck pipe. The manuscript describes a study performed to analyze the hole cleaning while blind drilling horizontal sections. Most of the losses while drilling across fractured or vugular formations happen sudden, and this represents a risk of formation instability and stuck pipe. Additionally, the cuttings accumulation may lead to a potential pack off. To understand the hole cleaning the annular pressure while drilling was introduced in different sections, what via change of the equivalent static and dynamic densities describes the cutting and cavings accumulation in the annulus. Additionally, the hole cleaning behavior with different fluids pumped through the drillstring (i.e. drilling fluid, water, water with sweeps) was studied. The proposed study was performed in 4 different fields, 9 wells, across horizontal 6⅛-in. sections with total lost circulation. It was identified that while drilling with full returns ECD vs ESD variations are within 1.5 ppg, those variations are matching with the modeling of hydraulics. Once total losses encountered the variations between ECD and ESD are very low - within 0.2 ppg - indicating that annular friction losses below the loss circulation zone are minimal. This support the theory that all the drilled cuttings are properly lifted from bottom and carried to the karst into the loss circulation zone and not fluctuating above the loss zone. Additionally, minor to no relation found in hole cleaning while drilling with mud or a water with sweeps. This finding also is aligned with the stuck pipe statistics that shows higher incidents of stuck pipe while drilling the with full circulation due to pack off. The manuscript confirms the theory of the hole cleaning in total lost circulation and application of different hole cleaning practices to improve it. The results of the study can be implemented in any project worldwide.