One of the most critical issues in TSP fields is the unconsolidated character of its sands. Historically, most of the wells drilled in TSP fields, including vertical, deviated and horizontal wells, have been completed with cased hole gravel pack (CHGP). However, over the course of the years, these completions have been known to fail eventually, especially in the case of horizontal completions. Among the failure reasons are the complexity of such operations and the drawdown applied during production. During the last drilling campaign in 2014, a horizontal well was completed with open hole gravel pack (OHGP). In addition to the change of completion, the production strategy was also modified to delay the water breakthrough and reduce the drawdown. These changes have significantly contributed to increase the production of the asset and opened the opportunity to apply these changes in wells for future campaigns. The horizontal well, was drilled through unconsolidated sand (Pliocene), where continuous fluid losses were expected to be encountered. During the well project execution it was necessary to create a mitigation plan in order to minimize the risk of fluid loss (rate) circulation before running the lower completion. For this it was necessary to include an isolation valve to control the losses once the packer was confirmed to be set. Normal reservoir pressure, and available facilities, was key factor to decide to include a gas lifting system in the upper completion which was also designed to have the maximum ID as possible for future intervention jobs such as acid stimulation and logging operations. Finally the well was successfully completed in OHGP with no signs of bridging. Based on the results obtained a complete detailed analysis for the pre and post job will be exposed in this document. This paper outlines the different challenges faced, as well as to highlight the action plans, mitigations and lessons learned encountered during the planning, design, and execution of the completion phase. In addition, a review of the production history of similar completions and the production strategies followed will be discussed. Finally, the results of this well will be summarized and lessons learnt shared.
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractThis paper describes the field evaluation of drilling strings with different stabilizing configurations, so that minimizes bit vibration problems in the bottomhole assemblies (BHA), contributing to optimize the performance. The studio was made for Lagotreco field, Block III in Maracaibo Lake. The evaluation is supported with simulation results obtained with drilling computer applications.The use of BHA designs with the criteria of stabilization "30-60ft" (stabilizers placed to 30ft and 60ft from bit, respectively), generally used in western PDVSA operational areas, to control straight holes and displacements; cause premature damages at the bits, such as broken cutters, chipped cutters, lost cutters and ring outs. These dull characteristics are potential signs of lateral vibration, increasing drilling costs because of additional bit trips.A dynamic analysis study of three different stabilizing configurations for BHA (30 -60ft, 15-45ft and 0-30ft), show the values rank for critical rpm speed, side forces and displacements measured from bit, for every case.The field test evaluation shows the reduction of bit damages by vibration effects, with a BHA stabilized 15'-45'; so that the decreasing of drilling time in terms of costs per feet (CPF). The study also includes an unconfined compressive strength formation analysis from the study area (USC).
Repsol (operator), together with partners Petrotrin and National Gas Company of Trinidad and Tobago, took over operations of mature fields Teak, Samaan and Poui (TSP) Offshore Trinidad at the end of 2005. With the intention of planning further development in the TSP reservoirs (comprising more than 10 vertically stacked main units, highly compartmentalized reservoirs with complex tectonic geometries) an indigenous comprehensive field evaluation was required. Thus, a sand-by-sand Screening Project was carried out with the main objective of identifying the reservoirs with maximum potential so as to direct further technical effort on specific reservoirs for early monetization of reserves.Based on the results of the sand-by-sand screening project, a prospect validation project for Teak Field was initiated -consisting of extensive field data acquisition, detailed interpretation and modeling workflows, adapted to the particular needs of mature fields. Several incremental opportunities identified during screening were validated and detailed modeling was performed to support further development. On completion of this effort, the company acquired a holistic view of the asset in terms of projects and its remaining resources, so a drilling campaign was envisioned and planning started.The selection of drilling candidates was not a straight forward process. The number of opportunities had been reduced considerably from the opportunity category to the actual well candidates. Several disciplines developed specific workflows to overcome the challenges, for example: risk assessment for infill opportunities and probabilistic forecasting (Subsurface), trajectory designs including anti-collision, drilling through depleted sands, torque and drag analysis and selecting a suitable rig for the field and production platform conditions (Drilling Engineering); among others.At the time of submitting this paper, two drilling rigs are moving onto the acreage to start drilling these opportunities by the end of 2013. This paper outlines the different challenges faced, as well as case studies of the evolution and maturation from the screening to the drilling stage of some of the prospects.
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractThis paper describes the field evaluation of drilling strings with different stabilizing configurations, so that minimizes bit vibration problems in the bottomhole assemblies (BHA), contributing to optimize the performance. The studio was made for Lagotreco field, Block III in Maracaibo Lake. The evaluation is supported with simulation results obtained with drilling computer applications.The use of BHA designs with the criteria of stabilization "30-60ft" (stabilizers placed to 30ft and 60ft from bit, respectively), generally used in western PDVSA operational areas, to control straight holes and displacements; cause premature damages at the bits, such as broken cutters, chipped cutters, lost cutters and ring outs. These dull characteristics are potential signs of lateral vibration, increasing drilling costs because of additional bit trips.A dynamic analysis study of three different stabilizing configurations for BHA (30 -60ft, 15-45ft and 0-30ft), show the values rank for critical rpm speed, side forces and displacements measured from bit, for every case.The field test evaluation shows the reduction of bit damages by vibration effects, with a BHA stabilized 15'-45'; so that the decreasing of drilling time in terms of costs per feet (CPF). The study also includes an unconfined compressive strength formation analysis from the study area (USC).
This paper highlights the value of seismic while drilling to successfully drill a vertical exploration well offshore Malaysia when faced with an expected pressure ramp in the shallow section and a gas chimney in the deeper section disrupting the surface seismic image data. Using a dual tool Logging While Drilling (LWD) seismic configuration enabled real time Vertical Seismic Profile (VSP) imaging and velocity data for accurate casing point selection, hazard avoidance and successful well construction and enabled elimination of a planned casing string. The seismic while drilling was conducted from seabed down to final well Total Depth (TD) to acquire a time-depth relationship for the entire wellbore. Acquisition was conducted during connections, an acoustically quiet period when the seismic shots are fired and downhole receivers in the seismic collar are recording. Transmission of the real time data starts when the connection is complete, and the mudpulse telemetry resumes with the drilling. Seismic waveforms sent to surface after each connection were processed for checkshots and VSP image successively after each seismic acquisition level. Critical 20 inch casing point was accurately set within 20m of identified hazards, despite an initial uncertainty of 100m predrill. The VSP image data was superior to the surface seismic image, recording clear reflectors within a disrupted gas zone, with better phase and frequency content. Full velocity profile over the whole well interval with 15m definition was acquired and processed. The character differed from the initial predrill model and offset well information significantly. Seismic while drilling removed the need for a pilot hole, and optimized the 20 inch casing point. Accurate real time velocity information allowed for accurate time to depth conversion for drilling decisions i.e. to assist in navigating the shallow pore pressure ramp, casing point setting and providing better seismic imaging in the gas chimney. This case study highlights one of the first applications of real time VSP data enabled by the use of two seismic tools placed 15m apart in the Bottom Hole Assembly (BHA).
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