Evolution of Frac-Pack Design, Modeling and Execution in the Ceiba Field, Equatorial Guinea

Proposal The paper details a study of fifteen frac-packs in twelve wells in the Ceiba Field, offshore Equatorial Guinea. Initial frac-packs were very unpredictable, experiencing numerous early wellbore screenouts and unpredictable tip screenout (TSO) behavior, placing proppant volumes of 10 to 160 klb with TSO net pressure increases ranging from 100 to 1,500 psi. The goals of this study were to: (1) develop a fracture modeling approach that would more reliably predict TSO behavior using mini-frac data, (2) develop reliable mini-frac analysis procedures and (3) determine the primary cause(s) of the early wellbore screenouts. The study resulted in improved designs, better execution procedures, more predictable TSO behavior and a reduction in early screenouts. After reliable analysis procedures were developed, it was clear that mini-frac fluid efficiency and net pressure varied dramatically in the Ceiba frac-packs, with efficiencies ranging from less than 5% to over 30% and net pressure ranging from 170 to 900 psi. After reviewing rock mechanical data and evaluating various fracture modeling approaches, the variations in net pressure were attributed to complex fracture growth due to high wellbore deviation and long perforated intervals (as opposed to differences in modulus). The combination of consistent mini-frac analysis procedures and a fracture modeling approach that included fracture complexity resulted in a much more reliable prediction of TSO behavior.