Rank wildcat wells in Ultra deepwaterD- present some of the greatest challenges today. Decision making during drilling is challenging due to a lack of offset well data. 3D Surface seismic data has significant uncertainty from the translation of two-way time to horizon depths which further induces risk into the predrill pore pressure model. This paper looks in detail at how the utilization of a high-tech logging while drilling suite in the execution of a rank wildcat enabled key drilling decisions to be made, reducing risk and time vs. depth plan the well. Seismic while drilling technology guided drilling in each section from spudding to total depth by allowing up to 600 m look ahead. This reduced target depths uncertainty from +/-100 meters to less than +/-5meters. Furthermore it permittedallowed this complex S-shaped well trajectory to avoid accidental penetration into the first target avoiding well control situation, placing the 13 3/8?? casing shoe safely above the first target, 80m shallower than planned. This ensured an increased mud weight window for the 12.25?? section. In the 12.25?? section, Formation Pressure While Drilling Technology was added to the Seismic and Sonic technologies to calibrate the pre drill pore pressure model. This was critical due to a narrow mud weight. The acquired formation pressures coupled with while drilling petrophysical data allowed for the pore pressure to velocity transform and normal compaction trend lines to be calibrated reducing the uncertainty in the pore pressure model ahead of the bit. Uncertainty in depth of targets and modeled pressure ramps ahead of the bit were further reduced with the Seismic data.
The emergence of formation pressure while drilling (FPWD) technology into the Gulf of Mexico (GoM) in 2004 was a step change for the industry. Over time the technology has been accepted by the industry as a reliable source for formation pressure and mobility measurements in real time for both reservoir evaluation and drilling optimisation. As the drilling frontiers are pushed, FPWD technology has advanced to meet the challenges. What have we learnt from this journey?Today, the technology is applied in an increasingly diverse environment in the GoM with a focus on safety and data quality. This has been achieved by a perpetual learning and development cycle, advancing FPWD technology, logging while drilling (LWD) technology and refining processes. Advances in Real Time capabilities in LWD have also become critical to allow fast and founded decisions.Examples are presented reviewing the applications and associated development of the technology over time to meet and exceed the GoM challenges:• Ultra deepwater, high pressure exploration in pressures exceeding 27k psi • Reservoir evaluation in the heterogeneous Wilcox formation, where mobilities can swing from 0.5 to 50 mD/cP in a matter of inches, result in poor quality or long stationary times when fixed rates and volumes are applied blindly; however integration of a intelligent pretest design that automatically determines optimal rates and volumes in milliseconds can turn failure into success • Sub salt drilling optimisation and pore pressure calibration • Testing in severe pore pressure regression and/or highly depleted reservoirs with overbalances in excess of 7k psi. Refining electronics and pretest motor controls opened up new opportunities for operators to determine magnitudes of depletion previously unobtainable • Shallow, unconsolidated or highly overpressured formations, which can lead to lost seals as the effective stress increase to the point of sand face failure, unique test designs perform low shock tests against the formation • Well to well comparisons for vertical and lateral connectivity required pressure gauge development in high pressure environments >20k psi High spread rates in deepwater GoM require the efficient application of these new technologies. Through application of lessons learnt and technology advancements, Non Productive Time (NPT) can be minimized and data quality maximized.
The Abiod formation is the principal target in the Miskar field, offshore Tunisia. Consisting of fractured geomechanically stressed carbonate with a measured matrix permeability as low as 0.1 mD. The formation dates from Campanian to lower Maastrichtian and forms a horst structure. The formation has been under production since 1996. Obtaining formation pressure data was considered critical for determining the magnitude of depletion from production, well-to-well comparisons for vertical and lateral connectivity, forward modeling, completion decisions, and refinement of the field development plan. Historically, this has been a challenge with conventional wireline (WL) formation testers for the following reasons: Severe depletion and well deviation causing differential stickingHigh temperatures (150 to 195° C) at the limit of tool electronicsLow permeabilityFractures and breakouts that can impact seal success This was overcome with a systematic multidisciplinary approach. After review of historical formation testing data, and influence on seal success with probe vs. packer elements, it was decided to apply formation-pressure-while-drilling (FPWD) technology. The key questions with FPWD in this environment are: Can we achieve a good transient profile and what is potential impact of supercharging? These questions were addressed with advanced prejob modeling, which enabled determination of an optimized pretest configuration and testing procedure to minimize potential supercharging effects. While drilling, stage-in procedures were used, and mud logging total gas data were gathered to identify areas of liberated gas. Pre-run wireline petrophysical data were gathered to characterize the Petrophysical properties of the reservoir and to calculate an intrinsic permeability profile. Ultrasonic borehole images and caliper data were used to determine the principal horizontal stress directions, fracture frequency, and orientation and to confirm the stratigraphic dipping of the structure. Combined, this information allowed a focused orientation of the FPWD probe and optimal station selection avoiding fractures and breakouts. This novel approach resulted in 100% seal success, >50% improvement. Four days of rig time were saved, and the required data were obtained.
The Abiod formation is the principal target in the Miskar field, offshore Tunisia. Consisting of fractured geomechanically stressed carbonate with a measured matrix permeability as low as 0.1 mD. The formation dates from Campanian to lower Maastrichtian and forms a horst structure. The formation has been under production since 1996. Obtaining formation pressure data was considered critical for determining the magnitude of depletion from production, well-to-well comparisons for vertical and lateral connectivity, forward modeling, completion decisions, and refinement of the field development plan. Historically, this has been a challenge with conventional wireline (WL) formation testers for the following reasons: Severe depletion and well deviation causing differential sticking High temperatures (150 to 195° C) at the limit of tool electronics Low permeability Fractures and breakouts that can impact seal success This was overcome with a systematic multidisciplinary approach. After review of historical formation testing data, and influence on seal success with probe vs packer elements, it was decided to apply formation-pressure-while-drilling (FPWD) technology. The key questions with FPWD in this environment are: Can we achieve a good transient profile and what is potential impact of supercharging? These questions were addressed with advanced prejob modeling, which enabled determination of an optimized pretest configuration and testing procedure to minimize potential supercharging effects. While drilling, stage-in procedures were used, and mud logging total gas data were gathered to identify areas of liberated gas. Pre-run wireline petrophysical data were gathered to characterize the Petrophysic of the reservoir and to calculate an intrinsic permeability profile. Ultrasonic borehole images and caliper data were used to determine the principal horizontal stress directions, fracture frequency, and orientation and to confirm the stratigraphyc dipping of the structure. Combined, this information allowed a focused orientation of the FPWD probe and optimal station selection avoiding fractures and breakouts. This novel approach resulted in 100% seal success, >50% improvement. Four days of rig time were saved, and the required data were obtained.
The objective of supplying real time LWD or FE information (Logging While Drilling and Formation Evaluation) should be to enable the client to make quick, accurate decisions on the formations being drilled, thus reducing and minimizing the geological uncertainty and maximizing or increasing the well bore exposure in the desired structure. During the course of drilling an 8 well Horizontal drilling program for the Kuwait Oil Company (K.O.C.) in the Burgan Field, Kuwait it became apparent that there was a need for clearer and better quality real time log information to enable the Drilling team to make quick decisions on were to place the well within the structure. This short paper will show the step change bought about in 3 of the wells drilled and the success and benefits realized by using long gauge PDC bits combined with a specialized short bearing pack motors, not only in the quality of the real time and recorded logs but in the over all bore hole quality as well. Introduction It was long recognized by the drilling hands in the 30's and 40's that running casing in vertical wells could be very problematic. One of the first theoretical attempts to explain what was happening down hole by Macdonald and Lubinsky in 1951 (Ref#1) gave rise to the "Crooked-Hole Formula". This basically recognized that a hole did not necessarily drill straight or in gauge and that the drift diameter of the hole could be significantly less that the diameter of the it that drilled it.
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