Successful Development of Thin Zones: Challenges and Strategies

Thin reservoirs that are only a few feet in thickness present a clear challenge to development specially when coupled with fractures, lateral heterogeneities, and structural uncertainties. This paper discusses the challenges associated with the development of a thin zone located at the top of a carbonate reservoir as well as the strategies implemented to overcome these challenges and develop the zone successfully. Due to the lower rock quality when compared to the underlying zones and extreme thinning, this zone could not be produced through the conventional vertical wells historically. Through the strategic monitoring program implemented in the field, an opportunity to place direct production from this zone has been identified specially in the mature areas of the field where the lower zones are fully swept after decades of continuous production whereas a thin zone at the top of the reservoir is unswept. Capitalizing on this opportunity, a strategic development plan has been initiated. This plan calls for placing horizontal laterals in this zone utilizing recently developed fit-for-purpose well placement and completion technologies. To successfully develop this challenging zone, several strategies have been implemented. First of these was strategic well planning where a systematic methodology was implemented to evaluate and develop this zone. The most promising target areas were located through comprehensive evaluation of the area, with detailed geological modeling. Secondly, advanced geosteering with a rotary steerable system (RSS) has been utilized to efficiently place laterals in the upper lobe of the targeted zone. Advanced completions, using inflow control devices (ICDs), were utilized as a fit-for-purpose to mitigate the counter effect of fractures and/or pressure differences across the horizontal section. The development program has been very successful in yielding significant production gains.