Geosteering is a proven concept which enables the delivery of productive wells by ensuring such wells stay within the target reservoir and sweet spot, and are precisely placed relative to fluid contacts. When reservoir engineering concepts are combined with Geosteering, quantitative estimates of the well's productivity can be determined to further evaluate the performance of the Geosteering and aid in decision-making. This workflow, applied in real-time, is called Real-Time Productivity Steering (RTPS).
This paper describes the application of RTPS to a horizontal well placed in a thin layer of oil reservoir. Prior to performing the real time productivity estimates while drilling, a prejob model was built, using offset well data, to estimate productivity from the planned well. Sensitivity analysis was performed on the trajectory, well length and some rock and fluid properties, to determine the plan that would result in optimum productivity for the well.
While the well was drilled, Logging While Drilling (LWD) information was used to update the existing model, geosteer, and perform productivity prediction while drilling. Productivity was predicted at three target depths: 8400 ft MD, 8800 ft MD, and at Total Depth (TD). The increasing liquid productivity index (PI) at the selected target depths were further justification to continue drilling until the predetermined TD.
The results at TD showed that the open hole liquid PI of the well in the sand of interest was about 63.8 stb/d/psi for a stable production rate of 1200 blpd. When completions were imposed on this single well reservoir model, it was predicted that the well will produce at a stable rate of 750 bopd. This was compared with a preliminary test done on the well where for the same well and reservoir conditions, the well produced 800 bopd.
This paper demonstrates that quantitative estimates of productivity can be made while drilling to complement geosteering. In addition to complementing and enhancing geosteering, RTPS provides a reliable dynamic model for subsequent completion design.
The RTPS workflow of complementing geosteering with reservoir engineering will enhance the ability to drill more productive wells as it will enable wells to be steered in the direction of maximum productivity, and also provide operators with sufficient information while drilling to make informed decisions for completions and for future wells.