Data Mining: Caliper Prediction Based on Gamma Logging While Drilling

Hole enlargement tools are often required in deep water drilling operations because of the necessity of running additional casing strings. At the same time, logging while drilling (LWD) tools are required depending on the drilling purpose even in large hole sections. When LWD and hole enlargement operations are required opening the hole and drilling with LWD at the same time offers an effective solution to save time and drilling costs. Deepwater drilling, hole enlargement and LWD operations are well established technologies individually. However, it becomes very challenging once these three factors are combined together. The main reasons of complication are hydraulics and vibration issues. Additional factors including deep water, large diameter hole, heavy LWD BHA's and reduction of flow to LWD tools by diversion at hole enlargement tools, may require a higher flow rate and higher pump pressure than the rig is capable of providing. Sonic LWD sensors are also sensitive to noise and vibration which are often caused by hole enlargement tools. In these most challenging of circumstances the operator decided to open the hole to 20? while simultaneously logging with LWD. This paper describes the procedures used at pre-drilling stage and actual operations such as the positive indication of the hole enlargement tool's activation and comparisons between surface weight on bit (WOB) / torque (TRQ) and downhole WOB / TRQ. The hole enlargement system selection and hydraulic optimization were the key points at the engineering stage. During the actual operation, it was crucial to monitor various drilling parameters and to keep the hole in good condition because of unstable formations. Although the hole enlargement service and LWD service providers were selected from different companies, detailed engineering and close communications were achieved for the common goal. The challenge ended successfully with hole enlargement to 20? while acquiring satisfactory LWD data for over a 1,100m section.

Evaluation of hole conditions is a key measurement for safe drilling and completion operations. Acquiring an accurate hole size measurement has been traditionally performed using wireline mechanical calipers deployed after drilling operations have been completed. This paper demonstrates how logging-while-drilling (LWD) ultrasonic sensors can be used to provide a time-lapse (4D) alternative azimuthal measurement of hole size, enabling data acquisition in different phases of drilling and tripping operations. LWD ultrasonic caliper measures the travel time and computes the tool’s stand-off to the wellbore wall. Acquiring azimuthal data around the wellbore during different logging passes enables acquisition of 4D caliper information. After being calibrated inside casing, the ultrasonic sensor provides azimuthal travel-time images, based on which minimum, maximum, and average hole sizes can be computed. Data have been acquired in drilling, trip-in, and trip-out modes and compared to wireline-oriented calipers. The data has been evaluated considering time-dependent deterioration, washout, and breakout developments. Recently introduced LWD slim ultrasonic imaging and caliper tools have multiple transducers and fast sampling rates. The hardware and algorithm design improves the hole size computation and wellbore evaluation. The tools provide a viable alternative to wireline mechanical calipers. While field data showed a good match in competent formations, differences between data acquired in multiple LWD logging passes and wireline mechanical caliper runs have provided 4D caliper information for evaluating time-dependent changes in hole conditions enabling future optimization of well construction. This paper illustrates the utilization of LWD ultrasonic sensors integrated as part of the drilling assembly to provide a 4D azimuthal measurement of hole size at different times, during drilling and tripping in and out of the hole.

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) operates the scientific deep-sea drilling vessel Chikyu for scientific studies on past climate changes, long-term crust transportation, biological and abiotic processes associated with hydrocarbon production, and earthquakes, the last being one of the most important research topics. Chikyu conducted the Japan Trench Fast Drilling Program (JFAST) to obtain core samples from sediment layers under the seabed for study on the large Tohoku earthquake which triggered the devastating tsunami in 2011. Chikyu has also started to conduct the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) as the Nankai Trough is one of the most active earthquake zones. As one of the primary goals of scientific drilling is to evaluate sediment properties, it is highly beneficial to characterize the lithology of the drilling layer during drilling operations. Even an approximation of these properties could potentially provide valuable information for conducting coring operations. Thus, a previous study attempted to discuss the properties of sediment layers using surface drilling data, and estimated the shear stress of the sediment. In this study, we summarize the method applied in the previous paper for estimating the torque at the drill bit from the surface measured drilling data for NanTroSEIZE deep riser drilling operation. This data was then used to directly calculate the shear stress of the sediment. The drilling torque at the bit differed from the surface torque, where this difference increased with increasing drilling depth. Our estimations of the drilling torque were validated using torque data obtained from logging while drilling (LWD) operations. We also used machine-learning approaches to predict the lithology, where learning data was created from surface drilling data and lithology information from core samples obtained during past scientific drilling operations. Machine learning was then applied using neural network algorithms by tuning the number of layers to create a predictive model. This paper discusses the preliminary attempt to predict the lithology using machine-learning approaches for NanTroSEIZE and JFAST data.

Data Report: Nuclear Magnetic Resonance Logging while Drilling, ODP Leg 204

Offshore oilfields are characterized by complex geological structure, such as presence of fault blocks, significant lateral changes of the rock properties. These features require accurate technology selection used during horizontal production wells drilling. Offshore drilling is fundamentally different from that on land, that requires a special selection of logging-while-drilling (LWD) technologies. The number of exploration wells is limited, therefore LWD tools and data interpretation should solve the problem of additional field exploration, that is impossible without advanced LWD technology application. Currently, LWD allows perform measurements similar to wireline logging – nuclear magnetic resonance logging (NMR), formation testing and obtain azimuthal density data. In addition, it is possible to perform measurements using reservoir-mapping-while-drilling service to solve geosteering tasks. This paper discusses examples of optimal well placement within the target zone, considering integrated interpretation of advanced LWD data for reservoir properties estimation, reservoir pressure behavior understanding, and choosing completion strategy. According to reservoir-mapping-while-drilling service data interpretation, density azimuthal data the geological model was updated. To clarify the petrophysical properties LWD-NMR data were used. These data allow to obtain porosity estimation, permeability, residual water saturation coefficient, evaluate bottomhole formation zone damage. Formation testing data were used to estimate reservoir pressure and hydrodynamic parameters of the target zone. Integrated interpretation of LWD data has been used to select the most optimal design of lower completion scheme and to control the development of reservoir.

Identification method for safety hazard behavior in offshore drilling operators

Reservoir navigation, often referred to as geosteering, is commonly used to optimize the placement of highly deviated wells. This technology has contributed significantly to the prolongation and economic well-being of mature hydrocarbon provinces around the world and been a major enabler for the commercial success of unconventional reservoirs. The reservoir information and analysis obtained during reservoir navigation is extensive and very valuable, yet is known to sometimes remain unused. Part of the reason is the complexity of reservoir navigation data and the limitations that many geosteering software applications cannot integrate the information provided from this data to update seismic-based 3D models. This paper demonstrates a fast and effective method of utilizing spatial reservoir navigation information to improve the three-dimensional understanding of producing reservoirs. Reservoir navigation interpretations from one or more wells can be used as inputs. The results include updated structure maps, refined gross rock volume (eg shale volume in unconventional reservoirs), updated values for porosity and water saturation and ultimately a revised volumetrics calculation. The results can be compared with calculations from other methods such as material balance and decline curves. Analyzing conflicting field data and reconciling them creates opportunities for improved drilling opportunities and better reservoir development. Datasets used in the paper show some specific examples of how the 3D workflows lead to better field developments with enhanced drilling operations and improving recovery factors. In the future, significant technical developments are expected in the type and complexity of reservoir navigation data originating from logging while drilling (LWD) tools. These data types will easily be included in the new 3D workflows without introducing undue complexity. Integrating reservoir navigation interpretations into sub-surface 3D models can be of benefit for real time drilling operations and also for field studies. The method uses a 3D workflow that can be completed easily and is fast enough to update models in real time. It is therefore useful for the purposes of improving architectural and geomorphological understanding of an area larger in scale than just the immediate active well. This creates an information rich environment with insightful information during geosteering real time jobs for better decisions. Additionally, the analysis method can be performed as a field study. This more comprehensive approach allows integration with other information after drilling operations have ceased to improve resource recovery and pick better future drilling targets.

Safety, efficiency, and reliability are at the forefront priorities when it comes to planning and executing drilling and completion operations. As an industry moving toward exploration and development in far more demanding environments and is consequently driven to find new and innovative ways to optimize drilling and well completion costs; The integration of RFID technology into the oil and gas industry is an excellent approach which has resulted in reduction of risks, operating time as well as increased operational flexibility. The use of RFID technology as a technique for remote actuation of downhole drilling tools has proven to be very effective over the conventional mechanical (ball-actuated) drilling tools enabling operators to run multiple remotely activated drilling tools on same drilling BHA while also maintaining full through-bore ID. Radio-frequency identification (RFID) provides a game-changing solution across a broad range of disciplines to maximize efficiencies and reduce operating costs significantly. This paper reviews a field application in which an RFID-actuated circulation sub was deployed in a multiple-assembly tool string to drill and simultaneously log a 6-in. hole section for a well in Karachaganak field. The risk of downhole losses in a 6-in. horizontal section (∼1,200-m length) in Karachaganak field led to separate drilling and logging runs. The main driver of adopting RFID technology in this application was the inability to retrieve a logging-while-drilling (LWD) radioactive source (RA) and also pumping high-concentration lost-circulation material (LCM), should downhole conditions dictate activation of a circulation sub. RFID-enabled circulation sub to eliminate additional trips of the LWD tool, as the previously deployed mechanically-actuated circulating sub would not allow access to the LWD RA because of its limited post-activated inside-diameter (ID) size. This requires additional time for tripping operations to change out the BHA in case of downhole problems, such as stuck pipe and total loss scenarios. Introducing RFID-enabled tool provided full through-bore access enabling RA retrieval while keeping the option for multiple activations of the circulation sub as per operational requirements thereby enabling the operator to immediately eliminate the additional trip for the LWD tool. In this case study, no downhole losses were experienced; however, the RFID circulation sub served to boost hole cleaning once total depth was reached as this operation required high fluid-circulation rates for efficient cuttings transport, especially in the avalanche zone of the well. Additionally, the full through-bore flow provided by the RFID-actuated sub enabled the client to displace the well with a high flow rate and therefore save significant time and costs on fluid displacement The adoption of RFID-actuated circulation sub improved drilling performance by enabling the operator to complete the entire operation in a single run and saved 4 operational days. The main objective of the system was to drill and log safely and efficiently to the target depth in one run and achieve high flow rates to enhance wellbore cleaning.

Handling drilling and production waste associated with oily contaminated drill cuttings, NORM and produced water is an environmental and economic issue in offshore drilling and production operations. There are a number of waste management options and subsea injection into suitable geological formations can be a preferred one. This is because it can achieve zero discharge operations; eliminating transportation and spill risks. It can also be economically favorable. Although subsea drill cuttings and produced water re-injection operations have been conducted in an environmentally acceptable manner, system design and operational experience are limited. A few worldwide drill cuttings re-injection operations from mobile offshore drilling units are reviewed first in the paper. Lessons learned from these and other system design and operational experience include a detailed subsurface study and careful engineering, wellhead and injection system design and effective communication to handle emergency disconnect, quality control on well integrity and slurry injection procedure. Challenges and best practice guidelines for waste injection operations from subsea wellheads are given to minimize failure and maximize success. Introduction Growing environmental regulations and constraints put pressure on drilling operations to find environmentally friendly and economically sound solutions for handling drilling waste. Drill cuttings re-injection (DCRI) operations into suitable geological formations have been successfully implemented all over the world.1–13 Figure 1 shows a schematic of DCRI process. Briefly, the drill cuttings from shale shaker are milled to small particles (300 microns or less), in the presence of water, usually seawater or other wastewater. The resulting waste slurry is pumped into sub-surface fractures created by injecting the slurry under high pressure into the disposal formation. Depending on drill cuttings generation rate, the waste slurry is injected either continuously or intermittently in batches. A continuous slurry injection scheme is expected to lead to an extended disposal fracture, while periodic re-injections would promote the development of multiple fractures and thus a compact domain of smaller multiple fractures from the wellbore. The batch process consists of intermittent injections of roughly the same volumes of slurry and shutting-in the well after each injection. This allows the disposal fracture to close onto the cuttings and to dissipate any build-up of pressure in the disposal formation. This may be impractical when re-injecting into low leak-off shale as the target disposal horizon when drilling rates and thus the slurry generation rates are relatively high. In practice, therefore, re-injections may shift from essentially continuous mode during drilling of large hole sections to periodic as the cuttings generation rate declines with the well approaching TD. Although drill cuttings re-injection has been applied since early 1980s, these operations have mostly been restricted to fixed platforms; annular re-injection into subsea wells, where drilling operations were in progress, had not been feasible until early 1993. BP, through a Drilling Engineering Association (DEA) JIP, conducted the first field trial DCRI operation in March 1993 into the annulus of a subsea well from a mobile offshore drilling module unit (MODU).14, 15

Integration of logging-while-drilling (LWD), nuclear magnetic resonance (NMR), and azimuthal acoustic tools with a geomechanical study resulted in successful drilling of the first horizontal Ratawi Shale well in Kuwait. This tool combination was used for the first time in Kuwait as a part of the bottom hole assembly (BHA), in addition to conventional formation evaluation tools, to acquire porosity without using radioactive sources. A deviated 8.5-in. borehole section of a well was planned through unconsolidated sand-shale sequences by kicking off from vertical and landing at an inclination of 90°. This geological section is typically crucial from a borehole stability point of view. Borehole deterioration and significant variations in pore pressure can create a high risk of becoming stuck-in-hole. The use of conventional porosity tools in a LWD BHA with installed radioactive sources would significantly elevate the risks to an environmental-hazard level. Additionally, even retrievable-based sources become problematic for successful extraction in high angle wells. Use of sourceless porosity was the perceived solution. LWD NMR and azimuthal acoustic tools, free of radioactive sources, were run for the first time in a LWD tool combination, with the primary objective to measure porosity, pressure prediction, and possible anisotropy using a centralized four-axis acoustic caliper. Previous experiences in the same geological setting encountered borehole enlargements by approximately 5 in. after only 15 to 16 hours. LWD helped bypass this issue and acquired high-quality data before borehole enlargement occurred. Additionally, indications of the presence of possible rock anisotropy were observed. The results were then correlated and matched to offset well data and existing field geomechanics knowledge. Well placement within a sweet spot of 6- to 8-ft thickness in the 6.125-in. lateral section was challenging and required the integration of at-bit measurements as well as distance-to-boundary geosteering tools to reach this objective. This paper discusses the planning, design, and execution using LWD, NMR, and azimuthal acoustic tools in this well. It also discusses the viability, integrity, and robustness of logged data as well as interpreted results. Optimization of real-time drilling operations and petrophysical data acquisition requirements are also investigated to improve future field development and overall reservoir management strategies.

The Iranian offshore drilling rig blowout occurrence on well SPDAA, which happened during the last run of a lengthy batch drilling operation on one of the South Pars stages, is cognitively analyzed in this paper. After 64 previous successful runs, the blowout happened, exposing a serious situation awareness (SA) breakdown on the part of the rig personnel. This study systematically assesses the crew's cognitive performance using the Driller's Situation Awareness (DSA) model created by Roberts, Flin, and Cleland (2015). It looks at how the crew interprets cues, understands well situations, and fails to foresee risk escalation. Inadequate danger anticipation, erroneous mental models, expectancy bias, and a lack of proactive intervention are among the cognitive deficiencies shown by the investigation, which are similar to those seen in the Deepwater Horizon accident. Similar trends of impaired situation awareness during crucial activities are seen in both events. The wider application of the DSA model as a training and diagnostic tool in offshore drilling operations is highlighted by this study. Stronger communication systems, better situational monitoring techniques, and improved crew training protocols are among the main recommendations, especially during the last stages of drilling operations when operational complacency and cognitive weariness may increase risk exposure. Due to its non-catastrophic ending, the Iranian offshore disaster garnered less attention than the widely studied Deepwater Horizon tragedy. As a result, interested firms and contractors did not conduct a thorough root cause analysis. The author revisited this event nine years later as the host and producer of a podcast about operational issues in oil and gas wells, and developed this study in conjunction with an episode of the podcast that looked at the occurrence. By using systematic cognitive analysis, this study fills the investigative gap and shows how thorough event investigation can provide important safety insights even in the face of imminent repercussions. These results help to enhance human dependability and safety culture in high-risk drilling settings.

Onshore field of South Sumatra basin are known as one of the largest oil petroleum systems in Indonesia. Its production rates are considerably high and healthy as there are multiple target layers of sandstone reservoir with sustainable pressure (Galih, et al.2023). This natural ease had levelled up the confidence to do extraction with factory wells design, means applying similarity of drilling operations (such as trajectories profile and BHA configuration) for several areas in the field. The significant amount of time in preparation was reduced with this method. The next level of time saving comes from maximizing the drilling operations in each well. The case study in this paper will elaborate the initial implementation of drilling technology known as intelligent rotary-steerable-system (RSS) push-the-bit to improve each well delivery time. Two types of wells, which represent the most common design of trajectory in this subject field, were selected to implement this novel technology. On a J-Type well with target inclination of ~ 22 deg, RSS capabilities are reviewed in the 12.25in hole section by gauging the performance in maintaining tangent interval of ~770 m. In a S-Type well with maximum inclination of ~18 deg inclination, RSS was evaluated in the 8.5in hole section on holding a verticality until the end of well for ~785 m. Both cases were having a comprehensive logging-while-drilling (LWD) suite consisting of gamma ray, resistivity, density, neutron porosity, pressure-while-drilling, and vibration mitigation tool. In addition, this technology is equipped with an automation platform which enables autosteer services to achieve precise steering with a reduced tortuosity borehole, while simultaneously increasing the rate-of-penetration (ROP). Offset wells analysis of each field had helped to form optimized configuration for the RSS. Identification of formation hardness, lithology lamination, loss, washout and tight hole hazard zones, reactive shales, and hard stringers were all considered in the optimization of RSS hydraulics design. Overcoming respective challenges, Target Well-1 has successfully achieved a significant ROP of ~65 m/hr with precise placement of 0.15 m center-to-center to plan and average dog-leg-severity (DLS) at ~0.5 deg/30m in the 12.25in hole. Laminated formation with massive change in strength properties, was a major challenge in this Field-G that may cause steering drift. Performance of automation platform plays a prominent role in achieving quick and adaptive control. Intelligent RSS ability of applying automated trajectory control, coupled with active machine learning algorithm had managed to secure precise placement in this well. In Field-B, Target Well-2 successfully achieved up to ~80 m/hr with 1.55 m center-to-center to plan and average of DLS 0.2 deg/30m in 8.5in hole. Excessive torsional vibration is a repetitive obstacle in this Field-B environment and has reduced the BHA outcome in several wells. The stability and consistency of RSS performance throughout this run had enabled a good quality borehole. intelligent RSS and the autonomous drilling platform predicting the optimum commands to create a smooth wellbore. A new benchmark was set in this entire factory wells project. These first runs in each field have proven the capabilities to push time and cost savings by applying novel technology in drilling operations. The case studies show the proven RSS can produce benefits of up to 3 times higher delivery time compared to the surrounding offset wells that utilize conventional mud displacement motor. Future applications towards the entire campaign may significantly be a game-changer in onshore drilling operations.

This paper presents technical features and associated benefits of a recently developed under reamer technology and its applications in the offshore Norway Oseberg South field to drill 12 ¼″ × 13 ½″ and 8 ½″ × 9 ½″ sections. It discusses the results of the operations and demonstrates how the operations benefited from the new technology. In today's drilling operations, expandable reamers are broadly used to support optimized casing and completion programs and to reduce operational risks such as high Equivalent Circulating Density (ECD), drilling troublesome formations and reaming well path conformities. The currently available hole enlargement technologies, such as ball drop and hydraulically activated reamers, carry intrinsic risks and limitations. To address the challenges associated with currently available under reamer technologies, expandable reamer technology was recently developed jointly by a service company and a major operator, and was field tested offshore Norway. The under reamer, which is fully integrated with the company's existing Rotary Steerable System (RSS) Bottom Hole Assembly (BHA), provides unlimited, on-command activation cycles, optimal placement within the BHA in multiple configurations and real-time feedback via mud-pulse telemetry. The feedback from the reamer includes confirmation of blade activation status, health of the tool, and vibration and stick-slip measurements. Because of the flexibility of its placement in the BHA, the reamer can reduce the length of the rat hole to a minimum of 4 m compared to the standard 30 to 70 m in the same drilling run, eliminating the need for a dedicated clean-out run. The reamer also enables reliable and unlimited activation / deactivation cycles with each cycle taking less than 5 minutes, saving operational costs for the operators. The under reamer was successfully deployed to drill challenging 12 ¼″ × 13 ½″ and 8 ½″ × 9 ½″ sections in the offshore Norway Oseberg South field. The 2497 m long 12 ¼″ × 13 ½″ section and 900 m long 8 ½″ × 9 ½″ section were both drilled to Total Depth (TD) in one run, with all requirements on directional control and Measurement While Drilling (MWD) / Logging While Drilling (LWD) met. The technology was proven to be a reliable and flexible hole enlargement while drilling solution that elevates drilling performance, reduces operational risks and lowers operational costs.

A formation inversion algorithm with real‐time performance and accuracy is crucial for natural gamma logging while drilling (LWD). However, traditional inversion algorithms are often limited by high computational resource consumption and insufficient accuracy. To address these issues, an improved forward method for natural gamma LWD is proposed. The inverse problem is subsequently modelled using the proposed forward method through which the search methodology and region of formation information are determined. On this basis, a collaborative fuzzy gradient neural dynamics (CFGND) algorithm is proposed, which combines the advantages of the collaborative mechanism in swarm intelligence algorithms and fuzzy gradient neural dynamics (FGND) to improve its accuracy and real‐time performance. Specifically, the collaborative mechanism is applied to conduct a global search using all possible formation information. Concurrently, the FGND algorithm initiates a local search from each particle and dynamically and intelligently adjusts the learning rate of the neural dynamics through a fuzzy logic system during the process to achieve rapid and stable local convergence. The CFGND algorithm subsequently updates its globally optimal solution using the optimal solution obtained from the FGND algorithm. This iterative process continues until the termination condition is met. Theoretical analysis proves the existence of an optimal solution for the inverse problem and the convergence of the CFGND algorithm. The results of simulations and experiments demonstrate that the proposed formation inversion algorithm features high accuracy and sufficient real‐time performance.

Digital oil and gas field is an overly complex integrated information system, and with the continuous expansion of business scale and needs, oil companies will constantly raise more new and higher requirements for digital transformation. In the previous system construction, we adopted multi-phase, multi-vendor, multi-technology and multi-method, resulting in the problem of data silos and fragmentation. The result of the data management problems is that decisions are often made using incomplete information. Even when the desired data is accessible, requirements for gathering and formatting it may limit the amount of analysis performed before a timely decision must be made. Therefore, through the use of advanced computer technologies such as big data, cloud computing and IOT (internet of things), it has become our current goal to build an integrated data integration platform and provide unified data services to improve the company's bottom line. As part of the digital oilfield, offshore drilling operations is one of the potential areas where data processing and advanced analytics technology can be used to increase revenue, lower costs, and reduce risks. Building a data mining and analytics engine that uses multiple drilling data is a difficult challenge. The workflow of data processing and the timeliness of the analysis are major considerations for developing a data service solution. Most of the current analytical engines require more than one tool to have a complete system. Therefore, adopting an integrated system that combines all required tools will significantly help an organization to address the above challenges in a timely manner. This paper serves to provide a technical overview of the offshore drilling data service system currently developed and deployed. The data service system consists of four subsystems. They are the static data management system including structured data (job report) and unstructured data (design documentation and research report), the real-time data management system, the third-party software data management system integrating major industry software databases, and the cloud-based data visual application system providing dynamic analysis results to achieve timely optimization of the operations. Through a unified logical data model, it can realize the quick access to the third-party software data and application support; These subsystems are fully integrated and interact with each other to function as microservices, providing a one-stop solution for real-time drilling optimization and monitoring. This data service system has become a powerful decision support tool for the drilling operations team. The learned lessons and gained experiences from the system services presented here provide valuable guidance for future demands E&P and the industrial revolution.