Completion Optimization while Drilling – Geomechanical Steering towards Fracable Rock for Optimal Selection of Stage Spacing and Cluster Density in Unconventional Wells

Abstract

The drilling of thousands of unconventional horizontal wells in North America highlighted the impact of the landing zone on production, underscoring the importance of geosteering with the intention of staying in the most fracable rock. Unfortunately, the use of fast drilling motors combined with delayed logging tools, and insufficient data to quantify mechanical properties while drilling created multiple geosteering challenges. This paper describes a new technology that uses surface drilling data to estimate, in real time, the geomechanical properties needed to guide the steering of horizontal wells into the most fracable rock. The Mechanical Specific Energy (MSE) computed from commonly available drilling data such as torque, rate of penetration and weight on bit has been widely used to improve drilling efficiency. However, the more recent use of MSE for completion optimization has yielded conflicting results. This paper introduces the use of Corrected Mechanical Specific Energy (CMSE) where the friction losses along the drill string and wellbore are computed and accounted for in real time. CMSE is used to estimate, in real time, geomechanical logs and build a live geomechanical model that is used for steering into the most fracable rock. Once the drilling is completed, the frac stage spacing and cluster density is adjusted according to CMSE outputs which include pore pressure, stresses, and natural fracture index. The new approach was used on multiple shale wells where the geomechanical logs predicted from CMSE and subsequently estimated fracture index were validated with multiple data including image logs, microseismic, and elastic properties derived from seismic pre-stack elastic inversion. This technology represents a major step in completion optimization since it tackles the problem and provides the solution during the drilling phase. A major advantage of the new technology is its ability to be deployed on any rig without the use of additional surface gauges, sensors or downhole measurement tools, avoiding additional costs and risks of potential wellbore problems. Additional benefits of the technology include: no on-site personnel or permits, the use of existing real time drilling data streaming services to quickly steer in the fracable rock, and having completion design immediately following the completion of drilling. This contrasts dramatically with alternative completion optimization methods for which data delivery, analysis, planning and design can take many weeks.

Surface Drilling Data for Constrained Hydraulic Fracturing and Fast Reservoir Simulation of Unconventional Wells

“…Ouenes et al [2] introduced the use of surface drilling data to simultaneously estimate the rock geomechanical properties, pore pressure, stresses, porosity and natural fractures needed to guide the steering of horizontal wells within the most frackable rock in real time, and additionally provide a completion design for optimal hydraulic fracturing when drilling is finished. The Mechanical Specific Energy (MSE) [3] computed from commonly available surface drilling data such as torque (T), rate of penetration (ROP), weight-on-bit (WOB) and bit diameter (D) has been widely used to improve drilling efficiency.…”

“…When using a motor, the MSE requires the use of the formula given below in Eq. (2) where N is the rotational speed of the drill pipe, Kn is the mud motor speed to flow ratio and Q is the total mud flow rate.…”