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.
Well construction process through the unstable formations prone to total losses, pack-off and water influx is challenging. The manuscript describes the casing while drilling (CwD) combined with stage-cementing tool as introduced solution, when the challenge was to ensure that torque limit is not reached while drilling and estimate the effect of CwD on curing total losses and bring the casing while drilling performance to the level of conventional drilling. Introduction of CwD required extensive study of the potential torque while drilling as existing stage-cementing tools have low torque rating. Additionally, the casing fatigue may be a factor affecting the operations what lead to an introduction of magnetic particle casing inspection. The CwD bit design was adopted to the geological conditions based on best performance of the PDC bit, and originally selected drilling parameters were further optimized based on the result of the first runs. As the drilling of the well required utilization of mud cap for well control purposes, the mud recipes were adjusted to optimize the drilling performance and minimize the cost implication. The proposed solutions allowed to eliminate the problem with wellbore instability and related stuck pipe events. Further the proper engineering of the drilling process allowed significantly increase the rate of penetration since the beginning of the implementation, when the drilling torque never reached the limit even at 7,000 ft depth. The manuscript describes in detail the approach to make a proper design of CwD process focusing on prevention of existing problems and aiming to convert mitigation tool to a performance tool. Additionally, in details described the studied effect of CwD on curing total losses in highly fractured environment.
Drilling the 12.25-in. landing section in one of the Middle East fields had been a challenge in terms of drilling performance due to combined downhole severe drilling dynamic mechanics effects and borehole instabilities. These complications eventually lead to downhole tool failures and a low rate of penetration (ROP). This manuscript describes the solution to introduce tandem downhole dynamic recording tools in the Bottom Hole Assembly (BHA) which provides a better understanding of the downhole dynamics and mechanics effects guiding to optimum BHA design and leading to better performance. Drilling the curve and landing section is challenging due to extreme stick & slip (S&S) and shocks & vibrations (S&V) phenomena resulting in low performance and difficulties in achieving the directional requirement. The 12.25-in. landing section is drilled with a full set of Rotary Steerable System (RSS) drive, Positive Displacement Mud Motor (PDM), Measurement While Drilling (MWD) and Logging While Drilling (LWD) tools, making the BHA very rigid. Nevertheless, many initiatives have been carried out to enhance the BHA and bit design with limited improvement. After performing a detailed risk analysis, tandem downhole dynamic recording tools were introduced to understand the downhole dynamics behavior and the interaction between the bit, the drilling BHA components, and the different formations drilled. The downhole dynamic recording tool is powered by batteries and records the data in memory mode for post-run analysis. It measures downhole drilling mechanics with its three-axis accelerometers, gyro, and temperature electronics along with other measurements. The downhole recording tools was installed tandemly across the 12.25-in. motorized RSS BHA where one tool was positioned inside the bit and another one in a sub above the mud motor. After the run, all the data from the two downhole recording tools were downloaded and then analyzed. From the recording tool at the bit, it can be concluded that the PDC bit used in the analyzed run, generated low-to-medium stick & slip, hence, a new bit design with more aggressive features could be used safely to enhance the ROP. From the recording tool in the sub above the mud motor, it was concluded that the BHA components and mainly the LWD tool created high-to-severe stick & slip due to its stabilizers, and action should be taken to minimize this effect. In addition, the drilling fluid lubricity needs to be enhanced to reduce the stick & slip and shocks & vibrations effects on the tools. All the presented solutions and lessons learned of the downhole dynamic recording tools utilization can be used for future run enhancement and to be replicated worldwide as applicable.
The current manuscript describes the engineering approach on how demanding wells in a very challenging field have been delivered more efficiently and consistently than the norm with an increase on the footage per day KPI by more than 75%. The subject field is one of the most challenging fields in the area with issues such as: top hole's losses with risk of cellar collapse; severe wellbore instability across 16-in. hole section with nearly 40% of offset wells facing stuck pipes; reactive shales across 12-1/4-in. hole section requiring enhanced drilling fluid design; losses across 8½-in. curve section, increasing the risk of not achieving zonal isolation after the 7-in. liner cementing job. A holistic approach was developed to tackle the field specific challenges including deployment of fit-for-purpose technologies, improvement in drilling practices and a better management of the risks. The wells delivered after the Implementation of this approach were drilled faster by up to 19 days when comparing with the previous drilling campaign, achieving ROP records in all the sections with significant improvement: 77% in 16-in.; 20% in 12-1/4-in.; 50% in 8-1/2-in.; and 60% in 6-1/8-in. The results can be taken as lesson learned when facing such challenges and be implemented in similar wells in Middle East and worldwide alike.
Carbonate formations around the world and specifically in a Middle East are prone to have total losses while drilling. And the nature of the losses often related to the highly fractured formations of the pay zone. When such fracture(s) is crossed by the wellbore the lost circulation initiated and led to a drilling without a return to a surface. To avoid undesired well control event or wellbore instability and to maintain the constant bottom hole pressure the mud cap drilling strategy often used as a preventative measure. The mud cap can be either the continuous or based on some volume or time interval, depends on the local practices or the policy of an operator. The mud cap flow rate as well as mud cap mud weight are often based on the best practices, not supported by an engineering study. To understand the behavior of the drilling fluid level in the annulus while drilling with total losses the drilling bottom hole assembly equipped with annular pressure while drilling tool was used. As the drilling required to use the continuous mud cap, then the specific guideline was developed on measurement of the bottom hole pressure and further conversion of it to the fluid level. The study was performed across pay zone with one or several loss circulation zones identified. As the result it was confirmed that the used mud cap flow rate had minor to none effect on the fluid level position in the annulus and that the bottom hole pressure remained the same. It showed as well that different loss zones are behaving in a different way, what can be considered as a factor affecting their ability to be sealed. The obtained knowledge and the information should help to understand better the loss circulation behavior as well be an important step toward development of the product which may cure the losses in high fractured carbonate formations. The results of the study can be implemented in any other project or a field.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.