Analysis of the deep drilling technology in unstable formations at the Semyrenky gas condensate field

The paper presents a general overview of deep drilling in unstable formations at the Semyrenky gas condensate field of the Dnipro-Donetsk Trough, including well design, bottom hole assemblies (BHA), drilling conditions, and drilling muds. Problems encountered during drilling for production casing of Wells 72- and 75-Semyrenky using high-speed drilling methods are analyzed. The relationships between the rate of penetration and disturbed rock stability, volume excess and depth, as well as consistent empirical patterns in changes in mud properties and depth are established. With these technical and economic performance indicators for well drilling are given, elements of a borehole stability management strategy were defined, the principles of mud selection for drilling through problem zones are validated. The paper discusses the requirements to a mud hydraulics program to reduce the erosion of borehole walls, specific borehole preparation techniques, such as reaming and gauging, for drilling in problem zones, and alternative options to ensure borehole stability. Keywords: borehole stability; statistical models; hole gauging; hole geometry; drilling mud; BHA.

NanoGram Detection of Drilling Fluids Additives for Uncertainty Reduction in Surface Logging

Manual sampling rock cuttings off the shale shaker for lithology and petrophysical characterization is frequently performed during mud logging. Knowing the depth origin where the cuttings were generated is very important for correlating the cuttings to the petrophysical characterization of the formation. It is a challenge to accurately determine the depth origin of the cuttings, especially in horizontal sections and in coiled tubing drilling, where conventional logging while drilling is not accessible. Additionally, even in less challenging drilling conditions, many factors can contribute to an inaccurate assessment of the depth origin of the cuttings. Inaccuracies can be caused by variation of the annulus dimension used to determine the lag time (and thus the depth of the cuttings), by the shifting or scrambling of cuttings during their return trip back to the surface, and by the mislabelling of the cuttings during sampling. In this work, we report the synthesis and application of polystyrenic nanoparticles (NanoTags) in labeling cuttings for depth origin assessment. We have successfully tagged cuttings using two NanoTags during a drilling field test in a carbonate gas well and demonstrated nanogram detection capability of the tags via pyrolysis-GCMS using an internally developed workflow. The cuttings depth determined using our tags correlates well with the depth calculated by conventional mud logging techniques.

Drilling Automation: The Step Forward for Improving Safety, Consistency, and Performance in Onshore Gas Drilling

In the current oil and gas drilling industry, the modernization of rig fleets has been shifting toward high mobility, artificial intelligence, and computerized systems. Part of this shift includes a move toward automation. This paper summarizes the successful application of a fully automated workflow to drill a stand, from slips out to slips back in, in a complex drilling environment in onshore gas. Repeatable processes with adherence to plans and operating practices are a key requirement in the implementation of drilling procedures and vital for optimizing operations in a systematic way. A drilling automation solution has been deployed in two rigs enabling the automation of both pre-connection and post-connection activities as well as rotary drilling of an interval equivalent to a typical drillpipe stand (approximately 90 ft) while optimizing the rate of penetration (ROP) and managing drilling dysfunctionalities, such as stick-slip and drillstring vibrations in a consistent manner. So far, a total of nine wells have been drilled using this solution. The automation system is configured with the outputs of the drilling program, including the drilling parameters roadmap, bottomhole assembly tools, and subsurface constraints. Before drilling every stand, the driller is presented with the planned configuration and can adjust settings whenever necessary. Once a goal is specified, the system directs the rig control system to command the surface equipment (draw works, auto-driller, top drive, and pumps). Everything is undertaken in the context of a workflow that reflects standard operating procedures. This solution runs with minimal intervention from the driller and each workflow contextual information is continuously displayed to the driller thereby giving him the best capacity to monitor and supervise the operational sequence. If drilling conditions change, the system will respond by automatically changing the sequence of activities to execute mitigation procedures and achieve the desired goal. At all times, the driller has the option to override the automation system and assume control by a simple touch on the rig controls. Prior to deployment, key performance indicators (KPI), including automated rig state-based measures, were selected. These KPIs are then monitored while drilling each well with the automation system to compare performance with a pre-deployment baseline. The solution was used to drill almost 60,000 ft of hole section with the system in control, and the results showed a 20% improvement in ROP with increased adherence to pre-connection and post-connection operations. Additionally, many lessons were learned from the use and observation of the automation workflow that was used to drive continuous improvement in efficiency and performance over the course of the project. This deployment was the first in the region and the system is part of a comprehensive digital well construction solution that is continuously enriched with new capabilities. This adaptive automated drilling solution delivered a step change in performance, safety, and consistency in the drilling operations.

A New LWD Dual Imager with Incorporated Feedback Improves Image Quality in OBM: Some Learnings form Abu Dhabi Offshore Carbonates

Recent developments in Logging-While-Drilling (LWD) technology have enabled high-resolution borehole imaging in oil-base mud that used to be a long-standing challenge. New applications to enhance image interpretation and maintain feature-integrity were developed with feedback from Abu Dhabi field examples of recently deployed LWD dual imager where hostile drilling conditions impacted the high-resolution ultrasonic image quality. The new dual imager has 4 ultrasonic sensors and 2 electromagnetic sensors (for resistivity image) mounted on a 15-ft sub in the drilling bottom-hole assembly (BHA). It provides ultrasonic amplitude and travel-time images at two central frequencies in addition to apparent resistivity images composed of four operating frequency measurements. A long lateral of around 8000-ft was drilled with this new imager through challenging heterogeneous carbonates and data was analyzed for geological interpretation. Based on the feedback for data quality improvement in certain intervals, the impact of shock & vibration on high-resolution (0.2") ultrasonic images was analyzed in time domain with simulated data first to understand the behavior of causative factors independently. Afterwards, the new algorithms were developed and deployed to maintain feature integrity of the data. The validation on field-data provided much-needed validation for the results in hostile drilling conditions. Resistivity images provided all the bedding and textural information (vugs, stylolites) with high confidence images at around 0.8" resolution. Higher resolution (0.2") ultrasonic images provided concrete information about vugs distribution for secondary porosity with quantitative interpretation on vug-indices. In addition, feedback provided from real time data was incorporated in subsequent processing and development of an image processing app that effectively fixes the depth-filtering related to drilling-induced events and stick-slip. Re-processing of the data provided high quality images that were used for high-resolution geological interpretation. Confident feature recognition was input into interpretation application hitherto available only in water-base mud while drilling. Results of this study with feedback incorporated to field-data from Abu Dhabi helped better the geological interpretation in hostile drilling condition as well, minimizing the need for e-line imaging.

Numerical Modelling and Analytical Comparison of Delamination during Cryogenic Drilling of CFRP

Carbon-Fibre-Reinforced Polymers (CFRPs) have seen a steady rise in modern industrial applications due to their high strength-to-weight ratio and corrosion resistance. However, their potential is being hindered by delamination which is induced on them during machining operations. This has led to the adoption of new and innovative techniques like cryogenic-assisted machining which could potentially help reduce delamination. This study is aimed at investigating the effect of cryogenic conditions on achieving better hole quality with reduced delamination. In this paper, the numerical analysis of the drilling of CFRP composites is presented. Drilling tests were performed experimentally for validation purposes. The effects of cooling conditions and their subsequent effect on the thrust force and delamination were evaluated using ABAQUS/CAE. The numerical models and experimental results both demonstrated a significant reduction in the delamination factor in CFRP under cryogenic drilling conditions.

Impact of Conventional Practices on Economic Efficiency as Illustrated by the Construction of Horizontal Sections of Multilateral ERD Wells and Fishbone Wells in Western Siberia

This paper is a detailed description of the first experience of an ERD wells horizontal section using ultra-low-viscosity drilling fluid as a drilling fluid implemented in the Russia land. This work has great value as an experience that allows to reevaluate the traditional views on the sole influence of drilling fluid parameters on the process of drilling wells. The thesis considers the key aspects and practices of improving the technical and economy values of drilling the multilateral ERD wells and FishBone wells in Western Siberia by applying an integrated approach based on three key factors: understanding the features of the rheology of drilling fluids; thorough analysis of the results of modeling wellbore washing and cleaning and comparing the calculated values with the actual values of the determined technological parameters in order to predict and control ECD; the collaborative work of the customer and the contractor, so-called "active supervising" methodology, aimed on making timely decisions for adjusting of the target requirements during the wells construction, "in situ" method, in order to achieve the made goals. The main conclusions have been made during the work: Effective and sufficient cleaning of annular space can be achieved with minimum values of drilling fluid rheology characteristics. Cuttings and marble bridging agent participate in the filter cake creation. The absence of marble bridging agent particles in the mud composition cannot be a reason of complications (absorption, sticking) when drilling low-permeability reservoirs. The concentration of the marble bridging agent should be determined, taking into account several factors: solids control equipment efficiency, formation permeability, density and drilling fluid composition. the recommended values for the parameters such as lubricant concentration and MBT, must be selected, firstly, based on comprehensive understanding of the idea of each parameter, and secondly, adequately assessing their significance under specific drilling conditions. Competent active supervising of drilling fluid has huge impact on the economy efficiency of well construction, whereas this approach can be beneficial for both the customer and the drilling fluid contractor. The implemented on the project approach allowed to save up to 60% for the cost of 1m3 of drilling fluid for horizontal section, as well as to reduce the time spent on the wells construction. The main result of the work: two multilateral wells were successfully drilled with the DDI of 7.2 and 6.55 and high risks of lost circulation. Wells construction was completed by running the liner to the target bottom without any signs of landings. However, the most important achievement is the emerging prospect of replicating the proposed approach to drilling ERD wells for deeper deposits development, that allows us to expect comparable technical and economy effects considering drilling conditions.

The 50th Anniversary of the Start of Drilling the Kola Superdeep Well

The Kola Superdeep Well (SG-3) is an outstanding achievement of Soviet science and technology, drilled in Precambrian crystalline rocks and reached a depth of 12262 m. It was one of a series of super deep wells planned within the framework of the program “Earth's Interior Exploration and Superdeep Drilling”. In order to achieve record depths, unique domestic drilling equipment and materials capable of working at high temperatures and pressures were created. A fundamentally new technology for drilling wells using hydraulic downhole motors was developed. Despite difficult drilling conditions and repeated acci-dents, SG-3 has fulfilled almost all the tasks assigned to it. The well was penetrated with full core sampling, which was subjected to comprehensive study. This made it possible to study the deep structure of the Earth's crust and to revise the interpretation of depth seismic data. It was found that changes in the physical properties of rocks at great depths had been erroneously interpreted as a change in their composition. It made it possible to assess the prospects of deep horizons of the Pechenga structure for copper-nickel mineralisation by uncovering a previously unknown body of ore-bearing hyperbasites. New information was obtained on the temperature gradient, which turned out to be significantly higher than expected, as well as on the vertical metamorphic zoning along the borehole section. The composition and physical properties of rocks in deep horizons were investigated. Tectonic fault zones and six types of ore mineralisation were identified in the borehole section. New data on ore formation processes at great depths have been obtained, which is an important contribution to the theory of mineral deposit formation

Simplified Solution for Managed Pressure Drilling - System that Drillers Can Operate

Until recently many of the wells on US land that were drilled using Managed Pressure Drilling (MPD) technology utilized one size fits all equipment designed for the offshore market. Since the cost and personnel requirements needed to run the offshore manifolds became a challenge due to market conditions and Covid-19 restrictions, the drillers sought a cost effective and simpler system to conduct their day-to- day operations. The challenge was to drill long laterals in Permian and Haynesville without losing the necessary MPD functionality that proved beneficial to reduce the risks associated with safety and to enhance drilling efficiency. For the MPD control system experts, the task was to correctly identify and automate MPD system’s functionality that would be of greatest use to the drillers to sustain their drilling performance. The concept of developing an easier to operate control system was undertaken wherein system accuracy and precision was maintained at the forefront of the development process. Electric motors/actuators and necessary drivers that could work directly on rig power were selected and tested. Control system logic that operates the chokes was modified to quickly adapt to the changes in drilling conditions, maintaining the necessary accuracy. This was done by studying and understanding drillers activities and behaviors like automated pump ramp down speed during connections, pipe movement during tripping etc. Specific MPD engineering charts, simple to decipher graphs, and necessary calculation tables were developed for the drillers to use for managing bottomhole pressures. Calculations which included specific schedules for spotting weighted pills were provided to maintain simplicity of the operations and something the drillers could easily execute. Today, many drillers are using this MPD solution to drill long laterals (Hovland et.al 2020). This trend is slowly leading to reduction of rig MPD personnel, especially during Covid-19, while the drillers are getting familiar with and operating MPD systems. A few of the crucial items that have allowed the drillers to run MPD on their own include MPD controls connected to drilling automation systems and the subsequent continuous revision of these controls based on understanding drillers tasks and needs. The use of electric motors enabled quick adoption to the changing drilling conditions while making connections, tripping etc. The furnished MPD calculations and graphs that drillers could follow for applying required MPD choke pressures kept MPD adaption simpler. The modifications made to the MPD choke controls geared towards facilitating necessary automation enabled the drillers to get trained in few days and operate the MPD systems while maintaining the same level of speed and performance.