Evaluation of New Stimulation Technique to Improve Well Productivity in a Long, Open-Hole Horizontal Section: Case Study

摘要

Saudi Aramco has significantly increased the number of horizontal gas producers over the past five years in an attempt to maximize well productivity through maximum reservoir contact while reducing the need for hydraulic fracturing stimulation, commonly required in most vertical producers. Although the majority of horizontal producers have met expectations, a good number of them have underperformed showing lower initial gas rates and higher decline rates than anticipated. The unexpected poor performance in most wells has been attributed to induced formation damage during drilling operations, the highly heterogeneous nature of the reservoir resulting in low porosity and permeability in different areas of the field, destabilization and precipitation of mineral and organic scales in the tubulars and formation, and condensate banking effects. The overwhelming majority of horizontal producers are completed open-hole, which significantly limits stimulation options once the wells have been completed and put in production. Moreover, high pressure and temperature conditions make accessibility of the horizontal section very difficult, and the chance for achieving successful stimulation of the entire horizontal section relatively low. Conventional stimulation treatments involving coiled tubing (CT) acid washes and bullheaded hydraulic fracture treatments have been attempted over the years but results have been mostly unsuccessful or relatively modest. This paper details a case history of a new approach combining different techniques, which was successfully used to stimulate a long open-hole horizontal section in an underperforming gas producer. A hydraulic fracture treatment using hydrajetting technology, that provided the ability to achieve deep penetration into the targeted zone, resulting in effective treatment fluids diversion, was successfully pumped. A detailed analysis to ascertain the effectiveness of the procedure was conducted, the results of which are discussed in this paper.