Mature Offshore Fields Rejuvenation Via Long Reach Wells and Massive Hydraulic Fracturing: the Kitina Case History

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, the capital expenditure associated to this kind of interventions of critical importance. It follows that the selection of the right and most remunerative well activities is crucial. In the Kitina Field, offshore from Pointe Noire, 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. From the Kitina field production increased of 80% reaching a production level lost since early 2004. This was achieved by infilling the Kitina South culmination with the long reach and ultra deep well KTM-SM5 and via a massive multistage hydraulic fracturing campaign carried out on the three wells draining the low permeability 3A reservoir. These represented the first applications in Congo of such technology. Eight hydraulic propped fractures were placed in three re-completed, cased-hole wells in the with very encouraging production improvements. A stabilized production increase ranging from 2 to 3 times was achieved. The paper describes the unique reservoir modeling, operation geology, and drilling, completion and production challenges encountered in the 2007 Kitina successful rejuvenation campaign. In particular, it focuses on the successful multi-stage hydraulic fracture campaign carried out on four wells of the Kitina 3A reservoir from the preliminary design and production forecast pre-job to the reservoir model history match and forecast phase postjob.