Modeling acid fracture conductivity to stimulate tight carbonates

  • Zhonghua Wang

    Student thesis: Master's Thesis

    Abstract

    Acid fracturing is a well stimulation operation commonly applied in low permeable carbonate reservoirs. Tight carbonates with high storability are good candidates for acid fracturing. The success of an acid fracturing treatment depends on the fracture penetration distance and the conductivity. This thesis presents a program integrating fracture geometry, acid flow field, fracture surface characterization and closure model to calculate the conductivity. A 2D fracture geometry model is used to give the fracture length and average width. Acid flow field is simulated by fully implicit method. Fracture surface is characterized by a geological statistical parameter and surface profile is generated by Matlab. A new closure model is proposed based on a 2D surfaces contact algorithm. The resulting conductivity is used to evaluate the incremental productivity. The effects of treatment parameters, fracture geometry, surface characteristics and closure stress on the conductivity are investigated. This work would predict conductivity and productivity at different condition and help to adjust the treatment parameters to give optimal productivity. Solution procedure developed in this thesis is summarized below: Step 1: Calculate fracture average width and half-length using fracture geometry model with reservoir data and treatment parameter input. Step 2: Simulate the pressure field of acid flow in the fracture space. Step 3: Generate fracture surface profile at the end of injection. Two rough surfaces are generated by Matlab based on the log normal distribution of fracture width. Step 4: Simplify the contact between two rough surfaces as contact between a rough surface and a smooth one. Step 5: Generate the fracture width profile with no closure stress by bringing the two surfaces into contact. Once the contact occurs, closure stress is no longer zero. Step 6: Calculate the fracture width profile after fracture closes with fracture closure model. Step 7: Calculate the fracture conductivity and incremental productivity. Keywords: acid fracturing, width profile, fracture closure, treatment parameter, conductivity.
    Date of AwardDec 2013
    Original languageAmerican English
    SupervisorMD Rahman (Supervisor)

    Keywords

    • Applied sciences
    • Hydrocarbon reservoirs
    • Oil wells
    • Petroleum engineering
    • 0765:Petroleum engineering

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