The Kitina Mature Offshore Field Rejuvenation: Massive Multistage Hydraulic Fracturing, Long Reach Wells, Improved Oil Recovery Techniques

Abstract

Many West Africa Offshore Fields are maturing and operators are completing secondary targets in their wells to maintain the economic operation of their valuable assets. However, off-shore environment makes the capital expenditure associated to this kind of interventions of critical importance. It follows that the selection of the right and most remunerative activities is crucial. In the Kitina Field, offshore Congo, deeper sands have been produced to economic depletion and reservoir studies allowed the determination of alternative production intervals for production maintenance. Large quantities of reserves can be found in low permeability, consolidated, formations as well as in very deep and remote culminations. During the first semester of 2007, the Kitina field production increased of 160% reaching a production level lost since early 2004. This was achieved with a variegate set of actions on different reservoirs:infilling the Kitina South culmination with the long reach and ultra deep well KTM-SM5,a massive multistage hydraulic fracturing campaign carried out on the three wells draining the low permeability 3A reservoir and 3rd) with the sweep optimization of the reservoir 1A. Eight propped hydraulic fractures were placed in three re-completed, cased-hole wells with very significant production improvements. These represented the first applications in Congo of different technologies opening a wide range of further applications in similar environments. The paper describes the 2007 and 2008 Kitina rejuvenation campaign with an eye to all the disciplines involved, from reservoir engineering and modeling, to operation geology, drilling and completion, production. The papers focuses with more detail on the successful multi-stage hydraulic fracture campaign from the preliminary design and production forecast pre-job to the reservoir model history match and forecast phase post-job. Interesting reservoir engineering overviews of the future development of the field via improved and enhanced oil recovery techniques are also presented. Introduction Existing oil and gas fields are maturing and new finds are more complex to discover and produce. In today's oilfields portfolio, mature reservoirs production maintenance and increase represent the biggest challenge to face over the next decades to meet the continuously increasing demand for hydrocarbons. Technology research, development and innovation have been the recent answer to sustain the world's oil and gas production and will continue to be so. However, new developments in technology need professionals who are taking the risk of testing them keeping in mind that the failure can be sometimes only a temporary and/or necessary stop towards the success. Mature fields can represent the "working ground" and "technological gyms" where to test new techniques with the final aim of accelerating and increasing reserves. Mature fields have to be seen today as opportunities for improvement rather than declining assets. Accurate candidate selection, optimized treatment design, sound reservoir modeling of production forecast represent crucial and interdependent factors for successful economic evaluations.

Enhanced Oil Recovery: An Update Review

“…Regarding gas injection, it is important to note that Cantarell/Akal represents the largest N 2 injection project in the world [214,278,279]. Similar to previous examples, most offshore environments are under continuous optimization strategies of gas and waterflooding to extend field production life and maximize oil recovery [261,[279][280][281][282][283][284]. Several EOR methods have been tested or have been proposed for offshore fields; however, only a few cases are listed in this review:…”

History Match and Reserve Evaluation of Hydraulically Fractured Wells: Low Permeability Field Case History

“…Due to the increasing oil price scenario in 2007, the three wells were hydraulically fractured in order to raise oil production [Ref. 1,2,3]. The stimulation operations were characterized by a high expenditure compared with the most common on shore treatments.…”