| Popis: |
The Llanito-Gala field, Colombia, is a structurally and stratigraphically complex field in which the determination of productive zones in multilayer shaly sands is hindered by a low-resistivity low-contrast (LRLC) condition. Data acquisition in this field is not straightforward and several operational problems have occurred during its history. Redevelopment of this mature field with over 40 years of production depended on obtaining funding for new drilling while competing against other projects in more prolific areas. Current technology cannot reduce the uncertainty in fluid identification for this kind of reservoirs, precluding the application of conventional methods for evaluation. The determination of objectives was performed using simple approaches, combining human knowledge with a multidisciplinary real-time work methodology as indispensable resources to minimize risk. Statistical analysis, probabilistic simulation and other basic techniques were used to determine ideal well locations and for outcome prognosis. Prior knowledge and experience acquired during drilling, discussed and analyzed by the team, were used to define well completion strategies. The fifteen wells proposed were divided into sets of five wells to allow continuous model update and flexibility in the redefinition of drilling and completion strategies. Designing operations accurately and ensuring the preservation of the integrity of the wells proved to be crucial factors in guaranteeing results in terms of oil production. An unexpected 80% of the sands drilled by the new wells corresponded to units not previously drained, increasing the field's proven reserves in almost 5 MMBbl of oil. All new wells are oil producers, and the oil production rate of the field was doubled. This experience, from the planning stage through to the final evaluation, is documented as a case study that can be used by other teams working under similar scenarios to learn from the strategy, efforts, errors, achievements and lessons learned. |
