Landing a Well Using Deep-Reading Electromagnetic Directional LWD—Can We Spare a Pilot Well?

Successful placement of a horizontal well requires accurate landing of the well in the desired position and orientation in the reservoir. Operators face operational and economic challenges in achieving accurate landing due to limited seismic resolution and uncertainty in the reservoir geological structure. The current industry practice for landing a well is to use real-time logging-while-drilling (LWD) measurements to detect expected signatures or markers and adjust the well trajectory before entering the reservoir using shallow depths of investigation LWD measurements. To improve landing, operators frequently drill pilot wells to delineate the local reservoir features, which can be a costly and risky solution, especially when drilling in deeper waters where operating costs are high. The introduction of an 81/4-in, diameter deep-reading directional electromagnetic (EM) LWD service with a radial depth of investigation of more than 30 m (100 ft) in Brazil addresses landing applications and structure delineation for 121/4 to 14 in. hole sizes. Using a multilayer inversion, the tool maps the formation structure in a corridor up to 70 m (230 ft) centered on the wellbore, allowing the target interval to be identified remotely and proactive trajectory adjustments to be made to ensure optimal landing. Without drilling pilot wells, four field tests executed in deepwater offshore Brazil clearly demonstrated the real-time landing capability of the deep, directional EM technology by mapping reservoir features 25 m (82 ft) away from the borehole and also detecting reservoir thickness up to 35 m (115 ft). Deep-reading directional EM measurements can be used to reduce the number of pilot wells that may be needed by providing a higher degree of confidence in the landing process compared to the classical pilot well and sidetrack technique. In addition, the deep-mapping capability of the service provides improved reservoir characterization, resulting in more accurate geological models and enhanced reserve estimates.