Comparing Effectiveness Between Cemented Plug and Pert and Open Hole Ball Drop Completion Assemblies to Ensure Optimal Multistage Fracturing Treatment and Well Performance — Field Examples

摘要

Developing gas reserves from relatively tight formations are conducted by the use of a multistage fracturing (MSF) technique that enables maximizing reservoir contact by creating multiple fractures along the wellbore. The key to successful MSF treatment is to generate independent fracture propagation and ensuring the bottom-hole treating pressure (BHTP) is maintained above the fracture closure stress (FCS) also sometimes referred to as the fracture gradient or minimal horizontal stress (c_(min)), for the fracture to propagate. Both the open hole (OH) multistage (OHMS) assembly and the cased hole plug and perforation completion (PPC) methods are applied for fracturing horizontal wells. Cement behind the liner in PPC provides excellent seal and isolation between stages that cannot be achieved using either mechanical or swellable OH packers used in OHMS. Failure to maintain complete isolation between stages will not allow stand-alone fracture propagation, thereby reducing the number of originally designed fracture stages. This will reduce contact area and well performance. PPC, on the other hand, depends on manually perforating reservoir intervals and missing the sweet spot due to any misinterpretation of the OH logs will misalign the perforation gun with the reservoir section, thereby reducing reservoir contact significantly, and consequently, gas production. The OHMS fracturing has proven very effective in the carbonate reservoirs when wells are drilled parallel to σ_(min) and completed with swellable packers. The chances of generating individual fractures are high and the open lateral allows gas flow into the wellbore directly in addition to the production through the induced fractures. The amount of gas flow through the OH section depends on the vertical permeability and how efficiently the near wellbore section is etched and cleaned by the acid pumped.