Thailand Joint-Development Project Delivers MWD/LWD Benefits
A joint-development project has delivered a high-temperature measurement-while-drilling/logging-while-drilling (MWD/LWD) suite rated for 200°C. Results to date are compared with previous performance in the Gulf of Thailand (GoT).
A joint-development project has delivered a high-temperature measurement-while-drilling/logging-while-drilling (MWD/LWD) suite rated for 200°C. Results to date are compared with previous performance in the Gulf of Thailand (GoT). The new suite required a complete redesign of printed circuit board (PCB) electronics in order to meet the temperature-qualification criteria of 200 hours at 200°C with a survivability of 210°C for 4 hours.
When the joint development of extreme-high-temperature tools began in May 2014, the goal of the collaboration was to eliminate wireline in wells with temperatures over 175°C. Historically, the need for wireline was driven by the requirement to identify hydrocarbons, measure reservoir properties, and book reserves in high-temperature wells; this was accomplished by using a wireline string consisting of gamma ray (GR), resistivity, formation-density, and neutron-porosity sensors. Because of the 175°C temperature limits of the available LWD technology at that time, there was no viable option to log these wells while drilling. This resulted in valuable rig time spent on additional trips to change out bottomhole assemblies (BHAs), mitigate temperatures, and run wireline to gather this data. This also increased the exposure to nonproductive-time (NPT) events, stuck wireline tools, or loss of data if these tools did not reach bottom. Thus, the requirement arose to log these wells while drilling to reduce days per well and improve data collection. To this end, the joint development of extreme-temperature LWD tools was initiated and staged in two phases.
Phase 1 was the development of a 200°C-rated mud-pulse telemetry system, a bore- and annular-pressure-while-drilling tool, a GR tool, and a thermal neutron porosity tool. These were jointly developed within a 9-month period. Thirty-two wells were drilled with these tools with zero NPT and only two minor failures in secondary sensors before commercialization.
A second phase of the development was endorsed to develop bulk-density and resistivity sensors to complete the triple-combo logging suite. This would ultimately deliver the principal objective of eliminating the need for running wireline. Phase 2 began in March 2015 and was given an 18‑month window to deliver final products. The sensors required a complete redesign of all electronics to meet the temperature-qualification criteria outlined previously. Ten PCBs were designed and tested.
The next step involved a thermal-vibration qualification by building up individual inserts, strapping them on a vibration table, and subjecting them to 15–20 Gs of random vibration while heated to 200°C. This harsh testing identified more modifications and redesigns needed until all inserts met these criteria. After completion of all testing, five complete prototypes were built and delivered on time and on budget in September 2016 to begin field trials.
Challenges in the GoT
Drilling operations in the GoT strive to deliver approximately 400 wells per year. With this target in mind, the days-per-well key-performance indicator is considered crucial to measuring the performance and tracking progress in the GoT. Before 2015, delivery of wells with temperatures above 175°C within this target was limited because of technology restrictions.
Directional MWD. The MWD system uses pressure-modulated mud-pulse telemetry to transmit surveys and tool-face values at temperatures up to 392°F and pressures up to 30,000 psi. The sensor uses orthogonally mounted triaxial accelerometers and magnetometers to provide rotating inclination and azimuth. The measurement range accuracy is ±1.5° for tool face, ±0.1° for inclination, and ±0.5° for azimuth above 5° inclination.
- Directional-drilling operations
- Supports extended downhole operations with a battery module that supplies redundant power
- Provides definitive directional and tool-face measurements
Bore and Annular Pressure. This sensor acquires real-time bore and annular pressures and downhole temperature measurements while drilling, wiping, or tripping out of the hole in temperatures up to 392°F and pressures up to 30,000 psi. The bore- and annular-pressure measurement uses a quartz crystal transducer with a 1-psi resolution to deliver ±7.5-psi accuracy with ±3-psi repeatability. The measurement range is between 0–30,000 psi, and data can be presented in pressure units or equivalent circulating density (ECD) and plotted vs. depth or time.
- Swab and surge monitoring
- Underbalanced and managed-pressure drilling
- Monitoring hole cleaning and detecting packoff
- Monitoring mud-motor performance
- Managing narrow mud-weight windows
- Monitors hole cleaning and cuttings transport
- Provides accurate hydrostatic and ECD data to optimize drilling, maintain borehole integrity, monitor early indicators of drilling problems, and minimize NPT
GR. This sensor acquires real-time GR measurements while rotating or sliding at temperatures up to 392°F and pressures up to 30,000 psi. The GR obtains American Petroleum Institute (API) gravity readings between 0 and 500 with an accuracy of ±2 °API at a vertical resolution of 18 in.
- Shale- and clay-volume calculations
- Well-to-well correlation
- Formation-top identification
- Depositional-environment analysis
- Conventional and unconventional reservoir identification
- Geosteering and well placement
- Eliminates time and costs associated with mud cooling, staging in the hole, and other temperature-mitigation operations in extreme environments
- Applies environmental corrections for borehole size, mud weight, and potassium concentration in real time
Density and Thermal Neutron Porosity. This sensor acquires real-time porosity, lithology, and fluid measurements at temperatures up to 392°F and pressures up to 30,000 psi. The porosity tool uses helium-3 tubes to measure the reaction between matrix and pore fluids and americium-241/beryllium neutrons to determine formation porosity. The density tool uses scintillation detectors to measure GR scatter from a chemical source mounted in the collar.
- Reservoir-porosity measurements
- Lithology determination
- Gas detection
- Pore-pressure evaluation
- Hole-size determination
- Delivers real-time and recorded bulk density, density porosity, neutron porosity, standoff, and caliper logs
Multifrequency Resistivity. This sensor acquires real-time multifrequency resistivity at temperatures up to 392°F and pressures up to 30,000 psi. The sensor provides phase-shift and attenuation measurements from three transmitter/receiver spacings and two frequencies to generate 12 fully compensated curves.
- Water-saturation calculations
- Geosteering and well placement
- Diameter of invasion measurements
- Vertical and horizontal resistivity measurements in high-angle wells
- Pore-pressure evaluation
- Well-to-well correlation
- Operates in air, mist, and foam environments and oil-based, salt, and freshwater muds
- Delivers resistivity data in thinly bedded, steeply dipping, invaded, or anisotropic formations
- Uses a truly symmetrical transmitter to minimize borehole effects and impedance drift
Tool Configuration and BHA
The tool configuration and BHA for the sensors contains three sections. The typical order is as follows:
- Top: Density and thermal neutron porosity (thermal neutron detector, density detector)
- Middle: Extreme multifrequency resistivity
- Bottom: Extreme directional MWD (gamma sensor, borehole and annular pressure, directional sensor)
Each tool’s configuration uses four primary and three secondary batteries to allow continuous acquisition of data for a minimum of 7 days. The purpose of having three tool sections vs. the conventional four tool sections is that the tool lengths now allow field engineers to make up connections offline with an adjustable gauge stabilizer or mud motor and stand by the complete BHA assembly, which reduces time spent online to make up connections before running in the hole.
At the end of the Phase 2 trial period, 47 high-temperature wells were drilled and logged successfully with the service. The complete system was commercialized in November 2017, and an additional 24 wells were drilled before the end of March 2018. This brought the total number of wells drilled with the complete suite in the GoT to 71. The total distance drilled with the suite during this period was 477,623 ft, with temperatures reaching 199°C.
The distance drilled at temperatures exceeding 175°C is 102,171 ft with more than 1,750 hours of operating time spent between 175 and 200°C. The longest distance drilled per well is more than 8,900 ft in the same drilling section.
Effects and Value Created
Before the introduction of the service, additional time was being spent on BHA trips, temperature mitigation, and wireline runs. Fig. 1 illustrates the comparison in the same challenging fields between wells drilled with extreme-high-temperature tools and all other wells. The suite, with other drilling-efficiency measures, played a pivotal role in reducing days per well. The average well time reduced from 12 days per well to 6 days per well.
In addition, the new tools have comprised one of several key contributing factors in establishing two notable drilling records: drilling the GoT’s longest well (17,559 ft) and breaking a 13‑year standing record for the longest single-bit run in the production section (8,952 ft) without any failures at a maximum temperature of 199°C.
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 191054, “Thailand Joint-Development Project Delivers 200°C MWD/LWD Triple Combination: Eliminating Wireline, Driving World-Class Efficiency, and Slashing Days Per Well,” by T. Kleawyothatis, SPE, and J. Pruimboom, SPE, Weatherford, and S. Dendandome, SPE, N. Pisarnbut, SPE, and P. Thipmongkolsilp, SPE, Chevron, prepared for the 2018 IADC/SPE Asia Pacific Drilling Technology Conference, Bangkok, 13–14 March. The paper has not been peer reviewed.