Several mature fields in the North Sea experience significant challenges relating to high pressures and temperatures accompanied with the infill drilling challenge of very narrow margins between pore and fracture pressures. To navigate these narrow mud weight windows, it is critical to understand the bottom hole pressure. However, in the cases of fractured formations above the target zones, severe losses can be encountered during drilling and cementing operations often leading to the inability to maintain a full mud column at all times and even threaten the ability to reach TD.
The operator therefore decided to investigate the use of a new acoustic telemetry system that could provide internal and external pressure measurements, (along with other downhole measurements) independently of traditional mud pulse telemetry in the drilling assembly. Real-time distributed pressure data essential to understanding the downhole conditions could therefore be provided regardless of circulation, even under severe losses or during tripping and cementing operations.
This acoustic telemetry network was deployed on several wells through multiple hole sizes and including losses management, liner running and cementing operations.
The initial primary purpose of running the network was the ability to monitor the top of the mud at all times, even in significant loss situations. As real-time data was acquired it became apparent that the data could also be used in real-time to aid and help quantify the actual downhole pressures. The use of this downhole data was modified and new calculations designed for simpler visualization of equivalent circulating densities at the shoe, bit and identified weak zones in the well at depths beyond the acoustic tools themselves. This data was used to manage the bottom hole pressure within a 300 psi mud weight window to ultimately enable the well to be delivered to planned TD.
The tool and calculations helped verify managed pressure connections and subsequent pump ramp up and down operations to minimize pressure fluctuations in the well. Additionally the data was used during dynamic formation integrity testing and to measure and calculate ECD at various positions along the drillstring and casing when downhole PWD measurements were unavailable.
This paper will describe how the implementation of new technology through the downhole acoustic network was deployed and the lessons learned in how the real-time data was used, changed and adapted in this particular well. Due to this deployment the acoustic telemetry network will now be used on upcoming equally challenging wells and its range of operations expanded to include drilling, tripping and liner cementing operations.
The last several years has seen an increasing trend toward more depleted reservoirs and more challenging wells with tighter mudweight windows. Managed Pressure Drilling has been employed in these challenging well conditions, however industry take up has been slow for a number of reasons including technical, economic and deployment related. Those wells that have utilized Managed Pressure Drilling have tended to focus on the drilling related aspects of well construction. However, other areas of well construction such as casing and liner running and cementing and completion installation are equally and in some cases even more technically challenging. One area that has potentially hindered the uptake of Managed Pressure Drilling is that in general, and in particular in the well construction operations outside of on bottom drilling there has been no access to real-time downhole data. In particular this is related to real-time pressure data. Whilst cementing, displacing or completing then multiple fluid types and densities may be circulating both inside and outside the drillpipe, leading to significant challenges in simulations and models derived from surface data. To overcome this a new acoustic telemetry and measurement network is being deployed in depleted reservoir and managed pressure drilling operations to provide real-time downhole and along string measurements of pressures, temperatures and weights. Real-time data case histories will be shown from the Gulf of Mexico and the North Sea illustrating how this is being used to drive real-time decisions during drilling, cementing and completion installation operations in tight margin windows, depleted reservoir conditions and under managed pressure drilling operations.
Hernandez, Julian (Weatherford International ltd.) | Arnone, Maurizio (Weatherford International ltd.) | Valecillos, Juan (Weatherford International ltd.) | Vives, Javier (Shell Exploration & Production Co.) | Vannoort, Roger (Shell Exploration & Production Co.) | Groves, Duncan (XACT, BHGE) | Hawthorn, Andy (XACT, BHGE)
Managed Pressure Drilling (MPD) technology was used to successfully drill challenging hole sections, and to run and cement casing strings for a deepwater campaign in the Gulf of Mexico. Because this technology offered the advantages of precisely manipulating the annular pressure using a statically underbalanced mud weight within a narrow pressure window, MPD was also employed along with real-time downhole measurements (from XACT), to run the lower completion assembly into the drilled production interval and perform downhole operations. For this specific case, the prognosed pressure operating window was around 100 psi, however; the actual window was found to be 50 psi when losses were encountered while drilling the openhole section through the target reservoir. Consequently, the completions operations required the most accurate modeling and planning to keep losses at an acceptable rate while avoiding an influx or formation collapse. MPD was utilized to precisely manage downhole pressures while running the lower completions assembly, displacing the drilling mud with completions fluids in the openhole section, and monitoring losses during the breaker acid job. A complex pump schedule was created by analyzing the pressure at several critical points in the open hole. Through back pressure management and high-resolution losses rate seen through the Coriolis flow meter, these losses were kept at a reasonable level to avoid breaching the pore pressure gradient and the wellbore stability limit. This paper describes the planning and execution processes that made this deepwater managed pressure completion job a success.
Reeves, Michael (XACT Downhole Telemetry Inc) | Smith, Douglas Grant (XACT Downhole Telemetry Inc) | Groves, Duncan (XACT Downhole Telemetry Inc) | Brehm, Andy (Anadarko Petroleum Corp) | Rovira, Scott Andrew (Anadarko Petroleum Corp) | Armagost, Ken (Anadarko Petroleum Corporation)
Sweeps are a commonly employed hole cleaning protocol during drilling operations. Typically consisting of elevated density and/or elevated viscosity fluids, they are circulated with the intent of facilitating the transport of cuttings to surface.
Traditionally, sweep effectiveness has been judged qualitatively via visual appraisal of cuttings flow at the surface shakers. While modestly useful, this limited analysis has not resulted in optimization of sweep programs and most operators still design sweep frequencies, volumes and types based on subjective observations. Real-time transmission of downhole pressure from a single location at the bottom of the drill string can be utilized to confirm the presence of a sweep in the borehole; however, such data reveals very little detail of sweep effectiveness. Continued use of ineffective sweeps may eventually lead to lost time events or opportunity time, including, lost circulation, stuck pipe, reduced drilling penetration rate, or the inability to run casing. These risks are elevated as the well's geometric complexity increases.
A unique acoustic telemetry network has demonstrated the ability to help in the design and management of hole cleaning operations. This network, comprised of nodes spaced periodically along the string, enables real-time visibility of string ID and annular pressure from multiple locations along the wellbore. This capability allows real-time analysis of many downhole pressure based events, including accurate measurement of sweep location, dilution and the volume of carried solids. Such visibility enables timely adjustments to sweep size and/or recipe to ensure the well bore is optimally cleaned.
The acoustic telemetry network utilizes a high-voltage broad-band amplifier coupled with a piezoelectric stack to generate modulated compression waves which propagate within the steel of the drill pipe. Multiple nodes, spaced periodically along the string, repeat this acoustic signal to the surface while introducing information from each location into the data stream. The acoustic telemetry functions regardless of fluid type or flow rate. Each acoustic node is packaged to provide a large, unobstructive through bore while still providing mechanical strength similar to that of the drill string within which it is positioned. The resulting network communication infrastructure can be deployed with minimal complexity and is virtually transparent to all rig operations.
This manuscript documents the field use of acoustic telemetry network technology in a horizontal drilling campaign, during which string ID and annular pressure and temperature data was acquired, recorded and transmitted to surface from five different locations along the length of the drill string. It describes, from service supplier and operator perspectives, the technology's well-site implementation, downhole performance and data capture capabilities.
For the first time, data collected along the drill string is used to deliver a quantitative analysis and interpretation of actual sweep behavior and downhole performance. Included are lessons learned and resultant changes in the operator's sweep program to optimize performance based on this unique information.