Ortega et al. demonstrated the application of hydraulic fracturing to control both sand production and asphaltene deposition by altering the flow regime. Hydraulic fractures with HSP (without screens or internal gravel pack) increased and stabilized oil production, reduced asphaltene precipitation, and eliminated sand production.
The North of Monagas giant field in Venezuela has been produced since the late 80-s. Depth ranges from 12000 to 20000 ft (3,600 to 6,000 m). Wells in the field have experienced early in the production cycle both problems of sand production and asphaltene flocculation. A multidisciplinary team was created to define ways to optimize production from the field.
The paper first addresses the methodology used to identify the source of the sanding problem, including extensive mechanical analysis of the formation, with tri-axial testing and sanding critical flow gradient analysis. The effectiveness of the initial strategies of optimization of choke size, and selection of perforated intervals and gun sizes is evaluated. The onset of asphaltene deposition was analyzed, and it was determined that most occurring problems were related to drilling and production practices.
To solve both problems, by modifying pressure drop and flow profiles, a hydraulic fracturing strategy was implemented in the field. Special care was given to the particular well conditions (close-by dual tubing completion, with potential risk of communication, thick and multi-layered geometry), in addition to expected high treating pressures and sensitivity of formation fluids to thermal shocks. A detailed pre- and post-fracturing well testing procedure was adopted which allows for an optimization of the fracture length, and comparison of results with predictions. Prior to the main fracture, calibration treatments were performed; calculated fracture heights were compared to the ones determined from temperature logs. A new technique to determine permeability from mini-fracs using the theory of impulse testing was also applied. Finally, production logging after the frac and a build-up were used to assess the validity of the predictions.
Author(s): Schlumberger Dowell, L. Ortega, L. Brito, Corpoven S.A.; K. Ben-Naceur
Paper Number: SPE 36461