Field Testing and Validation of a Mechanical Alternative to Radial Jet Drilling for Improving Recovery in Mature Oil Wells

Abstract

Abstract Short radius laterals, where a drilling tool is able to make a right turn in a cased wellbore and then penetrate some distance out into a formation, is an attractive technology for enhanced oil recovery for both existing and new field developments. Lateral holes with different geometries can penetrate untapped compartments, thin or by-passed pay, less permeable oil zones that cannot be sufficiently drained by conventional processes, and extend the effective radius of a well while reducing skin effects. A commonly referenced technology is radial jet drilling, where a specialized shoe is deployed in the well, a casing cutter cuts a hole through the pipe, and then a nozzle with high-pressure cutting jets is deployed on a hose at the end of coiled tubing. The technology has yet to become common in the United States, despite tens of thousands of candidate wells that could benefit from such a restimulation. Problems with jet drilling systems include: uncertainty in distance and direction of emplaced laterals; low available power to front-facing cutting jets, as most of the power has to be directed to rear-facing jets to keep the nozzle on the formation; and difficulties cutting hard formations and when encountering hard clasts. The objective of this study was to evaluate a newly developed technology for production enhancement from low-permeability reserves that utilizes a purely mechanical drilling string deployed on coiled tubing that is able to make a right-angle turn in a wellbore and drill a ~1.5 in. diameter lateral 30 ft or more into a reservoir. To study the technology, two wells were selected and stimulated. A simulation study for one of the field test sites, Millman field, a Grayburg/San Andres field in the Permian Basin, New Mexico, allowed a sensitivity study for optimization of lateral emplacements, optimal number of laterals per level, and allowed prediction of the impact of the recompletions. The prediction of lateral efficiency showed that the four emplaced laterals gave the best overall efficiency for enhancing oil production with 28.5% predicted incremental production in previously stimulated zones, and a 33.3% increase for previously unstimulated zones. Diagnostic techniques for monitoring lateral direction and placement based on small, chip-based gyroscope and accelerometer chips were developed and field-tested, verifying lateral emplacement during the field tests. The first test well saw ~40% increase in oil rate with emplacement of 12 laterals in three intervals. The second test well saw a 47% increase in production after 15 laterals targeted a previously untapped zone. This paper presents, discusses, and validates the drilling technology, the simulation models and results, the sensor development, and field-testing of those three technologies at two wells, with the emplacement of 27 total laterals with lengths of up to 32 ft.