PZIG At-Bit Inclination and Gamma Ray Service

Measurements for Accurate Geosteering

Operating directly behind the drill bit, the PZIG at-bit inclination and gamma ray service provides real-time measurements that reduce directional drilling risk in critical hole sections. The early indication of changes in lithology, delivered by the gamma ray log, helps to accurately land horizontal wells.

Geosteering solution

When used together with the PayZone Steering real-time forward modeling software, the service is an accurate, cost-effective geosteering solution that helps to optimize well placement and trajectory while drilling. The software combines the petrophysical data from LWD logs run in offset wells, the geological earth model, and the directional well plan to model the subsurface geology. By continuously correlating real-time MWD and LWD data (including that provided by the PZIG service) with modeled synthetic log responses, the program determines the position of the well within the geological sequence, predicts lithology ahead of the bit, and proposes adjustments to the well plan. The result is reduced tortuosity and dogleg severity (DLS), and early bed-boundary detection, leading to a shorter time to production.

Dual-sub design

The PZIG tool is composed of two subs:

• a lower transceiver sub (LXM) that houses a sensor package, batteries, and electronics to process dynamic inclination and gamma units measurements before they are transmitted via electromagnetic (EM) short-hop through the formation to the upper sub
• an upper transceiver sub (UXM), designed to be part of the PathFinder MWD HDS-1 directional tools. The sub takes at-bit signals and processes them for transfer, via the DataLink MWD real-time communication platform, to the MWD tool for mud pulse telemetry to the surface.

This dual-sub design makes the inclination and gamma ray sensors completely independent of the mud motor. The small, easily transportable, modular subs can be configured to operate with any type of mud motor power section or rotary assembly. Sensor reliability and operating life are not affected by motor reliability. In addition, operational decisions about the need for at-bit measurements are not tied to the availability of a suitably equipped motor.