completion quality (CQ)

1. n. [Well Completions, Shale Gas]

A prediction of how effectively rock may be stimulated using hydraulic fracturing. Completion quality (CQ) is an engineering assessment of factors that determine the effectiveness of hydraulic fracture treatments and includes the ability to initiate and create an induced fracture network, the degree of reservoir contact of the newly created fractures, the level of connection to the natural fracture system of those created fractures and ability of the stimulated reservoir to deliver gas or oil into the well.

Important factors that affect stimulation design include the rock’s mineralogy, porosity, mechanical properties, compressive strength and tensile strength. In addition, the presence and state of natural fractures, the in situ stresses and the formation pore pressure are input into the derivation of CQ. Mineral content, porosity and natural fractures determine the mechanical properties and strength of rock. The direction of the minimum stress strongly affects the hydraulic fracture propagation direction. The difference between the maximum and minimum stresses influences the amount of branching in the induced fracture network; a low stress difference favors maximal branching. Variations in the stress and mechanical properties between layers control the height of fracture growth. Pore pressure affects the stresses. Pressure from nearby hydraulic fracture treatments or pressure depletion from production in nearby wells can alter the stresses and influence the effectiveness of the current hydraulic fracture stimulation.