Near-Bit, Real-Time Measurements from an Innovative Ultra-Deep Electromagnetic Tool for Proactive Geosteering in Horizontal Wells

Abstract

Abstract In some reservoirs, where optimum well placement requires that a well be placed close to a formation or fluid boundary, changes in the position of the boundary need to be identified early to allow prompt correction of the well path, preventing the well from intersecting the boundary and incurring a costly side-track. Even if the angle between the boundary and the well is only a few degrees, the distance between them can change rapidly. If a tool measure point is far from the bit, a reservoir exit may occur before corrective action can be taken. An innovative, ultra-deep electromagnetic (EM) design, integrated with the rotary steerable system, places a sensor location 9 ft behind the bit. The novel system enables near-bit, ultra-deep azimuthal resistivity (UDAR) measurements, providing inversion results for the surrounding structure much earlier than existing ultra-deep EM systems. The new UDAR tool achieves an inversion detection range of over 100 ft, with the sensor measure point very close to the bit. This allows for earlier identification of changes in formation or fluid dip, facilitating proactive well-placement steering decisions. This paper investigates how the depth of detection of formation boundaries, the relative angle between the boundary and the wellbore, and the sensor measure point affect the ability to avoid hazards during well placement operations. There are common limits on the maximum allowable dog-leg severity (DLS) due to the need for later passage of the completion assembly through the wellbore. Early identification of any change in the dip of a boundary is therefore critical. The closer the sensor measure point is to the bit, the quicker this trend can be identified and the required remedial action taken, within the prevailing DLS constraints. In summary, the real-time UDAR inversion of the new system enables much earlier geosteering decisions than existing technologies, resulting in a significant advance in well-placement technology. Reducing or eliminating geosteering risks helps reduce overall well time, maximize the value of each well, and improve the overall efficiency of a field development.