Precise Inter-Lateral Spacing for Optimal Stimulation and Enhanced Production in North American Shale
Authors: Rassadkin Georgy , Ridgway Douglas , Dorey Jamie , Healy Carl , Moss Clinton 
Published: February 2020

The growing problem of well-to-well fracture interactions in North American shale plays dictates the need for more accurate inter-lateral spacing measurements. Conventional wellbore surveying techniques, such as magnetic or gyroscopic MWD and wireline measurements, cannot by themselves guarantee optimal placement due to systematic errors that dominate the uncertainty in well trajectory measurements. This uncertainty impedes optimal field stimulation and production modeling as the historical wellbore positioning data used in statistical analysis are inaccurate. With present commodity prices, the industry cannot afford suboptimal field development caused by inaccurate well placement. This paper is proposing the use of a commercially proven long-distance ranging system to minimize inter-well uncertainty for optimizing production development in shale plays.

The solution to the conventional survey uncertainty problem is to measure relative well-to-well position using a long-distance at-bit while drilling magnetic ranging system. The system consists of a highly sensitive alternating magnetic field receiver assembly in the adjacent well and a magnetic field source in the form of a magnetic bit sub in the drilling well BHA. The bit sub includes permanent rare earth magnets and generates a sinusoidal magnetic field when it is being rotated by the flow of drilling fluid through the mud motor or when the entire drillstring is rotated. The system does not replace conventional MWD sensors and requires standard survey data for calculating ranging results. These results are available live for realtime directional drilling decision making. In this paper, we analyze the accuracy of the system in related downhole projects.

The system surface test results agree with the accuracy of 5% of the distance between the drilling well and the offset well. This is a many-fold improvement in comparison to traditional surveying methods applied to a typical lateral well profile. The system has already been used on several projects of a similar nature and proved its effectiveness. The suggested methodology can identify the cause of interactions between wellbores due to proximity, which allows operators to implement measures to improve hydrocarbon recovery and mitigate financial losses from "frac hits".

The described technique eliminates the major part of the uncertainty in lateral spacing and therefore allows increased accuracy for reservoir stimulation and production modeling. The concept of relative position measurements using magnetic ranging methods has been around for a long time and has helped to avoid well collisions, create twinned wellbore pairs or intercept wells in the relief well, and for complex plug and abandonment applications. The purpose of this paper is to raise the attention of the industry to the described technique so the advantages of relative well placement can be applied for a better understanding of the growing problem of "frac hits" in North American shale plays.