With the increasing demand for more efficient drilling operations, the oil industry is searching for new ways of utilizing all data available while drilling. The integration of the realtime drilling information with data from offset wells and the reservoir model is considered of high value for accurate wellbore placement and geosteering. This paper introduces an original methodology to better understand and analyze the well position within the subsurface and to warn the end user when predefined geological and drilling events are appearing or prognosed ahead of the drill bit. The concept is called Geosteering Diagnosis. We identify a monitored trajectory as composed of a real-time and a project-ahead section. The bit and the MWD/LWD sensors are monitored objects attached to the trajectory. A number of targeted objects (i.e. horizons, contacts, faults, targets, planned and previous drilled wells trajectories, well and grid properties) are accessible from the 3D geological model. Rules can be defined based on the relationship between the monitored objects and any targeted objects. Various thresholds are used to identify events at the time of the drilling and alarms can be triggered on specific cases. The Geosteering Diagnosis is applied to a production well in the North Sea. The rules are used to monitor drilling against the predefined geological model. They provide quantitative information, which can be used to either update the geological model, or take actions regarding the course of the well. Introduction 3D visualization tools are today part of the drilling operation process, allowing a better communication and understanding between the experts of the asset team. Real-time data are integrated within the earth model and can be visualized in real-time operation centers. Measurement While Drilling data (MWD) and the Logging While Drilling data (LWD) are used to evaluate the position of the well, assess the physical properties of the rocks and fluids drilled, and analyze the behaviour of the drillstring in real-time. Positioning horizontal wells within few centimetres height of targeted areas is only possible because of the evolution of the combined drilling and logging technologies. From the kick-off point, through the landing area and within the reservoir it is critical to have the best possible understanding of the formations crossed by the drill bit. The LWD data provides that knowledge in real-time at a high resolution scale. An optimal decision making process will not only rely on a constant monitoring of the drilling data within the 3D geological environment, but also on an accurate understanding of where these measurements are performed along the drillstring. Some logging data can effectively be measured tens of meters behind the bit. Each of the physical property measured by the MWD/LWD tools can be defined onto the Bottom Hole Assembly by its distance from the bit. The experience shows that it is often difficult to measure the distances between a measurement point along the BHA and a particular object in the 3D geological model. But this knowledge is important for the asset team for taking actions regarding the update of the 3D earth model at the time of the drilling. A diagnosis approach was then proposed to constantly monitor and analyse the MWD/LWD information against the geological model and predict future trends of the data based on the project-ahead trajectory. The methodology relies on the definition of rules based on measured distances and property differences between tools on the BHA and objects of the geological model. By applying multiple thresholds on the rules it is possible to define different levels of warnings, which will help to identify and predict coming events. At the same time the project-ahead approach is used to predict when possible events will appear. The Geosteering Diagnosis can be an excellent tool to help validating the geological model update at the time of the drilling. A final objective, but somewhat far away at this preliminary stage, would be automated well follow-up and steering reducing on-site personal.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWith the increasing demand for more efficient drilling operations, the oil industry is searching for new ways of utilizing all data available while drilling. The integration of the realtime drilling information with data from offset wells and the reservoir model is considered of high value for accurate wellbore placement and geosteering. This paper introduces an original methodology to better understand and analyze the well position within the subsurface and to warn the end user when predefined geological and drilling events are appearing or prognosed ahead of the drill bit. The concept is called Geosteering Diagnosis. We identify a monitored trajectory as composed of a real-time and a project-ahead section. The bit and the MWD/LWD sensors are monitored objects attached to the trajectory. A number of targeted objects (i.e. horizons, contacts, faults, targets, planned and previous drilled wells trajectories, well and grid properties) are accessible from the 3D geological model. Rules can be defined based on the relationship between the monitored objects and any targeted objects. Various thresholds are used to identify events at the time of the drilling and alarms can be triggered on specific cases. The Geosteering Diagnosis is applied to a production well in the North Sea. The rules are used to monitor drilling against the predefined geological model. They provide quantitative information, which can be used to either update the geological model, or take actions regarding the course of the well.
The Geosteering of high tech horizontal wells through thin reservoir sections is always a challenge. If the entire operation of real-time LWD Geosteering is monitored in a virtual reality environment, a near reality wellbore drilling situation can be simulated through stereoscopic projection within a modeled reservoir for better understanding and interpretation of a complex problem. This has significant benefits in reducing the rig wait time for critical decisions. Additionally, it provides the tremendous advantage of using the expert multi-disciplinary team at the base thus reducing the risks of drilling a less than optimal well. The Mumbai High L-III reservoir is a highly heterogeneous multilayered carbonate reservoir on the continental shelf of western India in the Arabian Sea. As a part of ongoing redevelopment program, multiple horizontal wells are being drilled through thin productive layers. This paper describes a successful Geosteering application using the latest technologies to transfer, edit and analyze information in real time. Real-time LWD data were transmitted via the INSAT 3B satellite from the offshore drilling rig to the Virtual Reality Centre in Mumbai City, India. Seamless sharing of data between the service company and the Reality Centre was achieved using the recent WITSML 1.2 data transfer standard. Real-time LWD, seismic and drilling data were integrated to monitor the drilling progress. A pre-defined geological model was used to model the LWD data. The planned and actual well trajectories were continuously updated while drilling. The geological model was updated based on the comparison between real-time and modeled logs. Instructions regarding mid course corrections were conveyed to the drilling engineer at the rig. The technology helped to optimize the well path, maximize the productive interval and avoided unproductive rig time. Introduction Mumbai High is one of the most complex oil and gas fields in the world as well as the largest and most prolific in India. It is located about 160km from Mumbai City in the Arabian Sea on the continental shelf. The entire field is divided into two areas, Mumbai High North and South, separated by a low permeability barrier. The field has multi-layered reservoirs with the L-III carbonate the main producer. The production from the field commenced in 1976 and it has been produced 20% of initial oil as on today. The field is at a very mature stage of its life cycle. In order to accelerate production and improve the recovery factor, a detailed redevelopment plan was formulated where a large infill drilling program was planned to drain the bypassed oil with several dual producer and injector wells. The study area falls at the boundary of the gas cap in Mumbai High North where the upper stacks of L-III are gas bearing and lower stacks such as L-III-h are producing oil. The paper deals with a real time operation and model update techique in a virtual reality environment applied to a high tech well with a 700m planned drain hole. The well targeted the 6m thick L-IIIh layer which had an effective porosity of 22%. The LWD Geosteering data was acquired by a major drilling service company and was transmitted through INSAT 3B to the server at the Virtual Reality Centre. Using WITSML 1.2 (Ref. 1 & 2) the real time data was then streamed into the modeling packages to update and monitor the drilling process. The planned and actual well paths and the modeled and actual logs were presented in the 3D stereoscopic projection and on the seismic volume to be validated and interpreted by the multi-disciplinary team. Instructions were conveyed to the offshore drilling rig to incorporate mid course corrections. The main objective of this project was to geosteer the well through the thin carbonate reservoir using a virtual reality environment to make faster and smarter decisions. This helped to reduce rig wait time and maximized the chances of a successful well. Core Study and Electrofacies A detailed core study indicates the presence of Foraminiferal packstones and wackestones as the dominant microfacies in the L-III reservoir. These were inter-layered with calcareous, carbonaceous and nodular shales in most of the area. The porosity development is mainly secondary in nature, however primary porosity has been reported at places in coral fragments and in the matrix.
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