December 2021 /// Vol 242 No. 12)
Improving drilling and logging operations with a new measurement platform
Comprehensive new logging services focus on enhancing subsurface insight, optimizing drilling performance and ensuring consistent well delivery, to help operators minimize cost and risk while maximizing asset value.
The oil and gas industry is shifting toward increased automation, operations with fewer people at the rig-site, and digitalization, along with increased focus on sustainable operations. While measurement-while-drilling and logging-while-drilling services have long been used for directional drilling, well placement and formation evaluation, this shift requires changes and improvements in how these services are operated, and the type and quality of measurements they make. To address these challenges, Halliburton introduced the iStar Intelligent Drilling and Logging Platform to help facilitate the ongoing industry transformation, Fig. 1.
Halliburton designed the iStar platform to simplify complex operations, deliver automated and repeatable performance, and provide the high-volume, high-quality drilling and logging measurements that operators need to develop deep understanding of their operations and their assets, to maximize their economic value. The platform is fully web-enabled, allowing clients to manage their operation from anywhere at any time. The sensors on the platform provide the data that customers need to refine subsurface models and provide a deeper understanding of geology and fluids.
These data are also the foundation for data analytics and other data science techniques that are increasingly common in the industry. The platform is designed to operate across a wide range of drilling parameters, including high rotary speed and high torque, to help maximize the rate of penetration and minimize flat time. The integrated drilling dynamics, combined with continuous well positioning measurements, support drilling automation and data analytics with physics-based models and digital twins helping to optimize the current drill plan.
Finally, the iStar platform has more sensors in fewer collars, significantly reducing the length of the bottomhole assembly (BHA) and decreasing the number of connections that must be made on the rig floor. The compact footprint allows easy handling and quicker pickup with fewer people at the rig site, reducing HSE risks and environmental impact.
The initial launch of the iStar platform comprises three services that collectively deliver the measurements that operators need to accurately place their wells, understand drilling dynamics and BHA performance, and perform robust formation evaluation, Fig. 2.
The BaseStar Service is the foundation of the iStar platform. Just as smartphones integrate functionality that used to require discrete devices, such as cameras and GPS systems, BaseStar integrates the critical measurements that operators need for accurate well placement and drilling optimization into a compact 13-ft collar with increased data transfer rates, reducing impact on the critical path. The service delivers accurate geometric well placement through definitive static-surveys taken while making connections, along with high-frequency continuous inclination and azimuth measurements while drilling for precise steering and understanding of borehole tortuosity. It also can provide definitive-grade surveys while drilling with a spacing as low as 2.5 m.
High-resolution gamma-ray logs are included for correlation between wells, along with gamma-ray borehole images, to further reduce the geological uncertainty in real time and enhance well placement. The gamma-ray measurement has been characterized, using a methodology combining physical measurements with extensive computer modeling, to ensure a high measurement quality and close agreement with wireline gamma-ray services.
The comprehensive suite of drilling dynamics sensors delivers the complete package of information needed for improved drilling efficiency and optimizing rate of penetration without the need for additional collars in the BHA. Pressure, vibration, downhole weight, and downhole torque measurements give a full understanding of BHA performance and enable automated drilling solutions.
Additionally, integrated hole shape and annular-pressure measurements allow real-time evaluation of wellbore stability and effective control of the mud program to protect formation integrity and mitigate hole problems.
Resistivity measurements are the basis of many different solutions for customers, including fluid and formation characterization, anisotropy, bed-boundary detection, and even large-scale reservoir mapping in three dimensions. Resistivity services from Sperry Drilling have always been available through a modular approach, with the flexibility to run the right service for the specific solution and operator needs.
The ResiStar Service measures resistivity, using electromagnetic wave propagation at two frequencies (2 MHz, 500 kHz) and three geometric spacings, to give a robust, physically compensated resistivity measurement across a wide range of formation and mud resistivities. The service is built, using years of expertise in advanced downhole electronics and antenna design techniques gained in developing the comprehensive range of resistivity services that Sperry Drilling offers.
Advanced electronics isolation, combined with digitization of signals at the receivers, minimizes the effect of downhole noise on the measurement, improving precision and accuracy. The ResiStar service also monitors downhole mud resistivity. In combination with measurements from the BaseStar service, such as hole size, this enables environmental corrections, based on downhole data for best-in-class measurement quality in all drilling environments.
The LithoStar Service is an integrated nuclear logging tool, with a mechanical design and processing methodology developed to deliver high-quality porosity measurements for accurate reserves evaluations. It combines formation density, neutron porosity, and ultrasonic standoff measurements into a single 15-ft (4.5-m) collar.
The accuracy and precision of the electron density measurement are equivalent to that of wireline tools under the same conditions, with the added benefit of the measurements being taken while drilling before significant borehole degradation or fluid invasion can occur. This high measurement quality comes from two sources. First, the design of the tool optimizes the size of the detectors and the placement of shielding to maximize the count rates and improve precision. Second, the traditional LWD “spine-and-ribs” processing is replaced with a new algorithm that better represents the physics of how gamma rays interact with the formation than previous techniques. This new algorithm decouples the effect of lithology and density—giving a highly accurate density that is independent of lithology and a robust measurement of the photoelectric factor (PE), independent of any density effects.
Additionally, the service has multiple processing techniques available in real time to give the best measurement quality in different BHA orientations and borehole conditions. These techniques use either the nuclear measurement themselves or the physical standoff measured by an ultrasonic transducer with independent physics.
The LithoStar service is also designed to place the Helium-3 detectors used for the neutron porosity measurement much closer to the formation, minimizing the impact of borehole effects on the measurement and giving increased count rates for improved statistics and higher precision. This eccentric arrangement also introduces azimuthal sensitivity to the neutron porosity measurement.
The iStar platform has been deployed in multiple locations around the world, with close to 100 runs in a variety of geological environments, both onshore and offshore.
In the Middle East, an operator used the new platform in several challenging environments across a range of well profiles with abrasive formations and high vibration. The efficiencies around tool-handling and increased data transfer rates reduced the overall rig operating time. The operator recognized improved formation evaluation measurements, compared to other systems, particularly in the responses of resistivity measurements in both low- and high-resistivity formations. The comprehensive set of drilling dynamics measurements, combined with the ultrasonic caliper log, also provided clear insight into the impact of drilling parameters on wellbore conditions. This allowed real-time optimization of the drilling process and further reductions in the rig operating time.
An operator in the North Sea successfully ran the new platform in an appraisal well. High-quality gamma-ray, resistivity, density, and neutron porosity measurements gave a clear understanding of the lithology. The accuracy of the measurements was validated against a subsequent wireline pass. High-resolution ultrasonic and density images allowed the operator to identify the locations for formation pressure testing in the clean sand packages, overcoming the impact of spiraling and borehole washout which could have prevented effective pressure tests.
This information enhanced the operator’s understanding of the field for future development campaigns. The easy handling and shorter pick-up time of the iStar platform reduced HSE exposure of field personnel, while also reducing non-productive time related to BHA handling operations.
The first three services on the iStar Intelligent Drilling and Logging Platform have demonstrated the benefits of a modern measurement platform designed for the current needs and challenges in the oil and gas industry. Beyond this initial rollout, a constellation of additional services is in development with the same focus on enhanced subsurface insight, optimized drilling performance and consistent well delivery, to help operators minimize cost and risk while maximizing asset value.