In the depleted South Area of Ceuta Field, in Maracaibo Lake, several recent mature wells recompleted during a workover intervention, yielded unsatisfactory production results due to a combination of factors, all pointing to a severe near wellbore formation damage. During the workover intervention the well is controlled and killed to allow pull-out the old completions and run the new one safely. Formation fluids are displaced by completion fluids as a result of high pressure overbalance during the intervention. Conventional stimulation treatments to remove and overcome the formation damage have been unsuccessful in most of the cases.

Understanding damaging mechanisms was critical. Four main damaging mechanisms were characterized: damage generated during drilling and original completion operations, damage caused by previous perforating process, damage generated by fine migration during production and severe damage induced by completion fluids invasion during workover interventions. Another challenge to add was the multi-layer heterogeneity: the wells typically produce from multiple intervals having widely heterogeneous flow capacities.

Through an extensive analysis of wells and reservoir information a new approach was proposed. In these cases, rather than follow the common practice of treating all intervals as having the same average reservoir properties and formation damages, the stimulation program was customized, taking into account the individual properties and skin of each layer. An innovative technique consisting in creating a controlled and focused implosion in front of intervals proved to effectively and selectively remove near wellbore damage without the need of chemical fluids.

This paper describes, through cases histories, the new stimulation approach, including process analysis, modeling and optimized design using a specialized simulator. The implemented Implosion stimulation technique delivers skinless completions with more than threefold increase in production, exceeding normal expectancy for this type of intervention.