Innovative Drilling Strategy for Horizontal Wells in Triple Splitter Wellhead Arrangement: A Case Study From Rubiales Field in Colombia
Authors: Marino C. , Campos N. , Ledroz A. , Londono C. , Espitia O. , Villavicencio J. , Calderon A. , Sastre M. , Guzman L. , Real I. , Gonzalez H. , Mora L. , Caceres J. , Gaitan D. , Martinez S. 
Published: February 2024

Abstract
An operator in Colombia applied a splitter well arrangement for the first time to provide an optimal directional drilling design and execution strategy based on cutting edge surveying technology, data analytics, and a calibrated magnetic scan model. The drilling faced the challenges of potential well collision scenarios with pressure risk. Knowledge-sharing from the operation offers a benchmark for magnetic scan and trajectory design methodologies to aid in addressing complexities associated with directional drilling.
For the first time, the operator implemented gyro-while-drilling (GWD) technology with a solid-state sensor, specifically for surface sections. Optimal intervals for GWD and MWD runs were identified through a calibrated magnetic scan model. Data analytics and visualizations supported a safer design and execution of nine complex horizontal wells in a splitter well arrangement. This approach facilitated the continuous capture and application of lessons learned, enhancing the operator's well-by-well strategy. Pressure and collision risk challenges were effectively managed using a comprehensive exemption process and a robust prevention and mitigation plan.
Results from drilling in sequence from surface to production (not in batch), nine splitter wells have shown zero health, safety, and environment events, zero well collision events, successful wellbore departure with the inertial toolface of GWD, and effective directional control with geological targets achieved while preserving a safe separation distance between the splitter wells without need of trajectory replanning or increase of drilling risks. The GWD sensor was the primary surveying tool for the surface section in a 12 ¼-in. hole size. Measurement-while-drilling tools transmitted real-time data to surface. The azimuth measurements proved enough accuracy to be used as reference after being compared to GWD, even in the presence of high external magnetic interference. These measurements provided a benchmark for a well arrangement at low separation distance at the well reference point and demonstrated an acceptable accuracy to use MWD measurement at magnetic scan separation starting from 15 ft for the casing design used in this campaign. The magnetic scan model was an effective method to define the GWD interval for the well. These nine wells resulted in 60% land use reduction over conventional designs; the technical viability of the splitter well project is important for a more sustainable future of drilling operations in Colombia. This was the first use of the GWD solid state sensor in Colombia and the first splitter well arrangement for the operator. This case study from the Rubiales field leverages data to take right decisions and will provide practical guidance to engineers facing similar challenges in constrained drilling environments for sequential drilling.