An emerging technology called sourceless well placement and logging (without using traditional chemical radioactive sources) has intensified in recent years because of various factors, such as drilling risk reduction and cost optimization, as well as evolving government regulatory and health, safety, and environment (HSE) requirements.
Established technologies, such as acoustic sensors, have been tested during pilot projects in several Middle Eastern development environments to evaluate the viability of replacing conventional density-neutron sensors. Current developments and integrated workflows are encouraging for the provision of sourceless well placement, porosity, and petrophysical and geomechanical evaluations for some of the mature reservoirs. These developments include a substantial number of case histories already established in clastic and carbonate depositional environments for the previous five years.
The current well was planned through carbonate and clastic sequence as part of a geological section deemed important from a borehole stability point of view. Borehole deterioration and significant variations in pore pressure were also considered to increase the potential risk for the drillstring sticking. Conventional porosity tools used during a logging while drilling (LWD) bottomhole assembly (BHA) with radioactive sources exacerbate the potential risk at an environmental-hazard level. Additionally, retrievable-based sources can be problematic during extraction in high-angle wells. LWD azimuthal-acoustic tools free of radioactive sources were run for porosity measurements, pressure prediction, geomechanics, and possible anisotropy using a centralized four-axis acoustic caliper. A comprehensive petrophysical interpretation was also performed as part of the horizontal build section using acoustic porosities in comparison to its nuclear counterparts acquired in different modes. Permeability was deduced from acoustic and high-resolution microimaging data.
This paper discusses the planning, design, and use of acoustic tools as part of the BHA and the viability, integrity, limitations, and reliability of logged data and interpreted results. The integration of petrophysical data with cutting analysis is investigated to optimize real-time drilling operations and petrophysical data acquisition requirements for improvement of future developments and overall reservoir management strategies.
