Transverse Multi-Fracture Technique in Kitina Highly Deviated Off-Shore Wells

Abstract

Abstract Brownfield field have been defined as mature field in a state of declining production or reaching the end of their productive lives. Nevertheless these fields provide more than 50% of world's production as well as world's reserves and so it will be for next 20 years. For that reason revitalization of mature fields has to be a "must". The Kitina Field, offshore from Pointe Noire, Congo, is one such field. Deeper sands have been produced to economic depletion and, in order to maintain the economic operation of their valuable assets, alternative production intervals have been opened to production. Most of these low permeability reservoirs can produce at economic rates only with the application of hydraulic fracturing treatments in a multi-fractured well scenario. Accurate candidate selection, optimized treatment design, sound reservoir modeling of production forecast represent crucial and interdependent factors for successful economic evaluations. This paper describes the massive hydraulic fracturing campaign carried out between April and June 2007 on the Kitina 3A reservoir, offshore Congo. Eight hydraulic propped fractures were placed in three re-completed, cased-hole highly deviated wells with very encouraging production increases (stabilized production increase ranging from 2 to 3 times). The transverse multi-fracturing technique was adopted. This technique utilizes a series of packers and frac-ports that are sequentially shifted allowing continuous placement of more than one hydraulic propped fracture without shutting down the pumping equipment. All the aspects from candidate selection, pre-job design, on-site operations and post job evaluations with particular focus on the operational challenges encountered are described. Recommendations for the future applications of this stimulation technique are proposed. Furthermore, the challenging theme of forecasting mid-long term production profiles for horizontal, slanted and vertical multi-fractured wells is tackled. Different analytical and numerical models, approaching the task with various methodologies, were applied and tested to define the production profiles of the three candidate wells, which differ in terms of geometry and reservoir properties. On the base of the experience gathered on such wells, some general guidelines were drawn for a wider application.