Real-time Resistivity Images Using High Data-rate Telemetry in Papua New Guinea
Papua New Guinea has very complex geology due to its location at an active tectonic plate boundary in the Asia Pacific region. Low resolution seismic in the Papuan Fold Belt has led to a high degree of uncertainty in the structural geology which in turn makes identifying and targeting the location of oil and gas bearing reservoirs extremely challenging. High resolution borehole images from both logging while drilling (LWD) and wireline conveyed logging tools have been used to identify the presence and orientation of key structural features which aid in geological mapping and geomechanical modelling. LWD imaging tools such as the Azimuthal Focused Resistivity (AFR™) have been run in Papua New Guinea for more than ten years and the results have been critical for the project successes to date through an enhanced understanding of structural geology. Data acquisition using LWD has been preferred over wireline conveyance as the data is obtained soon after drilling whilst the hole has not been exposed for too long. Tectonic stresses and long formation exposure time can cause the well bore to deteriorate, making wireline runs operationally risky and often leading to poorer quality data impacted by borehole breakout. However, due to limitations with real time band width using traditional mud pulse telemetry systems, until recently only recorded LWD image data obtained ‘post-run’ has been available for interpretation. This meant any well path trajectory changes could only be made in the next hole section or after making dedicated trips to retrieve data. The decision-making process being reactive rather than proactive. On a recent development well in the Usano Field, a new, High Data Rate (HDR) telemetry system was introduced to allow real time transmission of larger data sets and higher resolution AFR images without sacrificing accuracy or negatively effecting the rate of penetration. This JetPulse™ HDR service also uses mud pulse telemetry but is capable of transmitting up to 18 bps of physical data. Traditional mud pulse telemetry systems were only capable of transmitting up to 3 bps. The new system enabled 16 bin real time images to be transmitted at >3 sample per metre data -density together with other formation evaluation and drilling dynamics data. The operator was able to perform accurate real time dip picking for enhanced early structural geological and reservoir understanding. The real time LWD image data compared well with recorded LWD image data, clearly identifying structural features such as bedding, faults, fractures, unconformities and borehole breakout orientation. The improvements in real time image data quality from faster telemetry have the potential to bring significant cost savings, reduced risk and improved efficiency in wellbore placement as the search for hydrocarbons in Papua New Guinea extends to increasingly complex locations.
AAPG Datapages/Search and Discovery Article #90371 © 2020 AAPG Asia Pacific Region, The 1st AAPG/EAGE PNG Geosciences Conference, PNG’s Oil and Gas Industry: Maturing Through Exploration and Production, Port Moresby, Papua New Guinea, February 25-27, 2020