Precise Interlateral Spacing for Optimal Stimulation and Enhanced Production in North American Shale

Abstract

Summary The growing problem of well-to-well fracture interactions in North American shale plays dictates the need for more accurate interlateral spacing measurements. Conventional wellbore surveying techniques, such as magnetic and gyroscopic measurements while drilling (MWD), cannot guarantee optimal placement due to growing systematic errors that dominate survey uncertainty. This uncertainty may impede optimal field stimulation modeling because the wellbore positioning data used in the analytical calculations are inaccurate. Multiple industry technical papers demonstrate a correlation between interlateral spacing and the severity of frac hits. The interlateral distance measurements are used in the calculations for optimal reservoir stimulation and frac hit modeling. With present commodity prices, the industry cannot afford suboptimal field development caused by inaccurate well placement. In this paper, we compare the conventional survey technique with a commercially proven long-distance active magnetic ranging system that supplements the traditional MWD system. We apply relevant survey error models to two exemplary well pads—an actual well pad from a West Texas shale play and a realistic, although hypothetical, example—and compare them with relative ranging uncertainty. The first example shows that MWD positional error exceeds relative ranging uncertainty while the wells are still near vertical at approximately 6,500 ft measured depth (MD). The second example shows that interlateral spacing uncertainty using active magnetic ranging can be 50% of the MWD semimajor error at the end of the curve at 10,000 ft MD [8,910 ft true vertical depth (TVD)] before the lateral section starts. The MWD uncertainty then gets larger due to systematic survey errors multiplied in the “dead reckoning” computation process. With the magnetic ranging applied while drilling, the ranging uncertainty stays practically the same throughout the whole well, enabling tenfold improvement in interlateral spacing accuracy.