Horizontal, heterogeneous reservoirs of low permeability present various challenges and drilling risks. The likelihood of encountering potential problems can be greatly increased when there is a minimal understanding of geology and pressure regime in the area of interest. A similar case was tackled while drilling an observation well.
The drilling challenges were carefully recognized and highlighted to be properly addressed. Planning and risk mitigation measures included the introduction of a set of drilling and tripping practices to minimize potential risks while drilling the well. Details of the comprehensive evaluation program and logging tools were discussed along with drilling fluid design. In addition, rigorous efforts were exerted on BHA design, drilling dynamic modeling, torque-and-drag simulation, and hydraulic management.
The integrated planning and drilling approach implemented in the subject well has ensured the safety of drilling operations through real-time formation pressure evaluation, which has allowed for quick mud weight control while drilling. In addition, the drilling fluid was pre-treated with sized bridging materials to build an impermeable filter across the anticipated streaks of permeable intervals. Improved drilling and tripping practices have helped in drilling a trouble-free well, where the risk of differential sticking was minimized. An advanced well-engineering software was used to design the rotary steerable system (RSS) and the logging-while-drilling bottomhole assembly to reduce the severity of stick/slip vibration and minimize wellbore contact across the lengthy BHA. This has led to an enhanced and optimized drilling performance, which was complemented by real-time monitoring to allow for on-the-spot decision making. The collected data in the well will help in identifying and modeling reservoir characteristics in terms of porosity, permeability, formation pressure, and fracture identification.
The employed integrated planning and drilling approach has successfully enabled meeting the objective of a challenging well in which a high level of uncertainty was present. The delivery of the well will help in making better reservoir management decisions and increasing the confidence in geological and petrophysical models.