After completing the drilling phase of the 8½″ section for a well in a giant mature field offshore Abu Dhabi, due to geomechanical challenges it was not possible to run the 7″ liner in a shale formation which was open for a long period of time due to rig repairs (top drive failure in open hole), exposing all reservoirs and compromising the field development strategy. After several unsuccessful attempts to run the liner and leaving a drilling BHA in the hole during one of the cleanout runs, it was decided to sidetrack around the fish to intersect the original 8½″ open hole section in order to recover the original hole and isolate the reservoir flow units from each other, which was critical for the field development since more than five reservoir layers were opened with water and oil bearings increasing the risk of damaging the reservoir integrity due to potential cross flow. Detailed measurement-while-drilling (MWD) survey analysis was conducted for the original hole in order to enhance surveys accuracy and minimize positional uncertainty. Typical survey management practices were implemented for Sag and Drilling String Interference; other techniques such as Dual Inclination, In-Field Referencing, and Multi Station Analysis were also applied. The implementation of these different survey management practices and their respective results are covered in detailed in the current article. Comprehensive planning was carried out, the sidetrack was accomplished and the original hole was successfully intersected at the first attempt. The advanced applied survey management techniques were crucial, particularly in the absence of magnetic ranging as the interval to intersect was open hole. The outcome of these corrections resulted in a shift of 8ft to the final well position, ensuring the correct direction and position for a successful attempt to intersect the well. This intersection was particularly challenging as the original hole had a 3D profile, thus it was critical to minimize both vertical and azimuthal uncertainties. Intersection was achieved with an RSS BHA, and the success of this intersection without magnetic ranging capability was only based on following a planned well trajectory that intersected the original hole surveys, clear validation of the accuracy of the surveys for both original and sidetrack holes. Achieving this challenging directional drilling goal allowed the completion of the well as per original plan, which was critical for the field development plan of these reservoirs. Based on the fact that there is very limited existing literature covering similar cases to the one presented, this current case represents a solid successful reference to be replicated in similar cases in the future covering these challenging applications of advanced survey management techniques.
Wellbore surveying is critical while drilling in order to assure the drilled well is following the plan and is penetrating the geological target. Additionally, wellbore surveying is the key to allowing a well to be drilled safely, avoiding other wells drilled in the same field, and optimizing reservoir production. Standard wellbore surveying accuracy is increasingly inadequate for optimizing the well placement in real time to maximize the reservoir recovery due to maturity of the field. The other disadvantage of the standard wellbore surveying often requires running an additional wellbore surveying tool to improve the accuracy in order to manage the collision avoidance with nearby wells in the same field, introducing unwanted time and costs. Hence, this article presents the advanced wellbore surveying technology that is successfully implemented in offshore fields of Abu Dhabi to overcome the limitations of the standard surveying accuracy without compromising rig time. Magnetic measurement while drilling (MWD) surveys are common standard and utilized in every directional well in this operation. To overcome the standard accuracy limitation, advanced survey correction to the magnetic MWD surveys is introduced. This includes in-field referencing to provide a higher resolution magnetic reference to calculate a more accurate well direction, correction to the effect of the steel components in the bottom hole assembly on the magnetic MWD surveys, correction to the errors associated with survey sensors calibration, and correction to any misalignment between the survey tool and the wellbore. Correcting the surveys in real-time while drilling is the key to placing the well accurately and to avoid offset wells in the close proximity. The details of the corrections methodology are discussed. Advanced magnetic survey correction procedures in real-time are outlined and mapped out. Finally, results of improving the magnetic surveys while drilling in placing the wells and minimizing the collision risk of offset wells are presented. This advanced survey technology allows drilling previously un-drillable wells in these offshore fields, and the allowance for increased density of wells in the reservoir gives the operator opportunity to maximize production recovery and extend the life of reservoir. Higher accuracy of wellbore surveys is an increasing requirement in mature fields to safely allow more accurately placed wellbores with the required production rates. This allows for improved well placement along the trajectory facilitating adjustment at control points and landing points to maximize the hydrocarbon production. In addition, it allows controlling the probability of collision with any nearby wells. The enhanced wellbore surveying accuracy is achieved by advanced magnetic survey corrections in real time. This is controlled by a stringent novel process and communication protocol in order to meet the accuracy objectives.
On several occasions during drilling, the drill string or in cases of liner job the liner string comes across an overall regressive environment. By regressive environments, the condition of the well bore returning to its unconditioned and in some cases unstable phase, is implied. The objective of this paper is to see how the regression impacts the circulating pressures in particular and how best to anticipate such conditions to optimize/modify the practices. The circulating pressures in deteriorated/reverted cases start showing spikes in the actual values well beyond the predicted models subsequent to same flow rates at the same depths. Such deviations in the actual vs theoretical values can pose severe complications for the drilling and liner jobs. These resultant complications however can be countered with the help of hydraulic mapping and gel envelope estimation in conjunction with optimized tripping and circulation practices for the respective operations to ameliorate the conditions. This paper explores the impact of regressive hole conditions ranging from constraints, operability, mechanical loads and fluid regimes. It builds upon that impact and delves into how best to utilize the tool of hydraulic mapping for smooth tripping and drilling operations in conjunction with the real time monitoring to define the operational envelopes. Delving into the dynamics of the hole conditions in regards to tripping and drilling operations across open hole, the paper seeks to build upon experience and reach an optimized mantle for tripping, drilling, circulation and conditioning operations in compromised hole conditions without any time delay or complication. During the life span of the well operations, the open hole well bore conditions of the wells become adverse to continuing onwards with the operations without at first conditioning or changing the downhole states altogether. This is the modus operandi for the majority of operations but in instances where the ambient impact is time sensitive or where the operations altogether are too complex and constrained for that to be done, the well conditions worsen, and the complications related to the ongoing operations increase manifold, rendering the operation in extreme cases unfeasible altogether. This likelihood can however be circumvented with the help of preventive intervention tools such as hydraulic mapping. There is no broad stroke solution to operational complications though, techniques and tools vary with each instance and are very case specific in both spectrum of definition and application. The most significant take away though, is how the incorporation of hydraulic mapping ensures the impending operational problems and complications are efficiently and specifically managed without any downtime or operational delay, on the fly. There are cases when the hydraulic and dynamic parameters have been mapped with upper limits built within the model yielding successful execution of operations against odds. In presence of rapid gelation or excessive gel breaking pressures against high differential formations, the practice of rotating prior to circulation or reciprocation prior to circulation are also determined with this tool. Real time operations monitoring also play a pivotal role in benchmarking and tracking the operational parameters of interest that are critical for operations. In order to achieve that however, there needs to be a composite model for the real time broomstick to be in place that reflects the overall picture of the open hole well bore. The hydraulic mapping technique requires minor inputs from the routine operational practices but forms an integral tool that can help execute operations effectively in jeopardized environments, against staggering odds without forfeiting any of the operational parameters or objectives.
The main objective of this study is to validate the market variations and the adoption of disruptive technologies effects on Drilling Operations through the analysis of Directional Difficulty Index (DDI) for historical and current wells with a common framework, allowing demonstrating the variations caused by the deployment of disruptive technologies as well as the impact of the market behavior. The methodology used here is predicated upon three main steps: First, historical drilling data for exploration and development wells for Abu Dhabi National Oil Company Offshore has been evaluated using the Definitive Survey listings. Second, this data has been correlated against the market historical data and with the introduction of disruptive new technologies that have dramatically changed the technical limit as well as in the standard operational practices has been observed. Third, a detailed analysis has been made of the correlations of market and introduction of technologies with their impact in the complexity of the wells. The study is an attempt to document correlation of the following elements to the main parameter analysed i.e. the directional difficulty index: Oil and gas market behaviour towards a direct impact in the complexity of the wells drilled:▪ During market downturn, the complexity of the wells is reduced▪ During the market uptick, the complexity of the wells increasedIntroduction of new disruptive technologies have a direct impact in the complexity of the wells, we focused on three technologies that changed the traditional practices increasing the technical limit, and its effect on the directional difficulty indexTwo additional observations were considered relating to the directional complexity index:▪ The development stage of the field: green or mature and its effect on the complexity of the wells▪ The field structure which determine the development strategy: i.e. drive line or rim developments and its effect on the complexity of the wells This study involving market behaviour, the introduction of new technologies and how they affect the directional difficulty index is a maiden attempt in its league; determining this correlation helps to better address the influence of these elements in long term strategic planning and predict change. In addition, if the findings associate the development stage of the field and the field structure with the directional difficulty index, this opens the door for future studies to better determine their influence.
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