Method for drilling a borehole

摘要

In a method for drilling a borehole real time geosteering data, including natural gamma ray data is obtained for a plurality of borehole positions for drilling a borehole along a projected trajectory. A formation layer having a thickness equal to or greater than the natural gamma ray sphere of influence and having a first lithology is identified. Data is processed for subsequent borehole positions. Upon location of the boundary of a formation layer of different lithology within the natural gamma ray sphere of influence, at least two points of the different formation layer boundary are determined by using the inverse problem methods, and an extrapolation ahead of the drill bit of at least two points is made utilizing the boundary to determine whether to change the borehole trajectory.

主权项

1. A method of drilling a borehole, wherein the drilling tool including a gamma ray tool providing gamma ray data within a natural gamma ray sphere of influence, the method comprising the steps of:
a) selecting a target formation layer in a formation, wherein the formation includes formation layers having different lithologies; b) proposing a borehole trajectory to the target formation layer; c) drilling the borehole and obtaining real time directional and natural gamma ray data at multiple borehole positions along the borehole trajectory; d) processing the real time directional and natural gamma ray data for each of the borehole positions; e) locating a generally horizontally extending boundary of the target formation layer, wherein the boundary is located between the target formation layer and an adjacent formation layer having a different lithology; f0 determining whether at least two data points of the boundary of the target formation layer are located within the natural gamma ray sphere of influence; g) using the data points to extrapolate the location of the boundary of the target formation layer ahead of the drilling tool; and h) adjusting the borehole trajectory based on the the extrapolated location of the boundary of the target formation layer to maintain the borehole within the target formation layer.