Hydraulic fracturing treatment is one of the major contributors to increase oil and gas production. In most areas, fracturing has remarkable impacts on gas potential and sustainability. Proper design and implementation of fracturing technology and calibration of fracturing parameters provide significant technical and economic advantages. The minifrac treatment conducted before the main hydraulic fracturing, is a tool often used to conduct some essential evaluations of the treatment properties and optimizes the design before the main treatment. Minifrac treatments are also used to understand the reservoir parameters such as well transmissibility that allow making final modifications to the actual fracture design.
The minifrac operation is part of the hydraulic fracturing process that consists of creating and propagating a small fracture using the same fluid that would be used in the main fracturing treatment to observe and measure pressure behavior and calculate hydraulic fracture parameters such as the instantaneous shut-in pressure (ISIP), fracture closure pressure, critical fracture initiation rate, fluid loss coefficient, and the rate and pressure necessary to extend and propagate the induced fracture. Minifracs are also widely used to assess formation properties, such as reservoir permeability and leakoff characteristics. These properties are important for characterizing the reservoir, conducting approximate assessments to evaluate well potential, and optimizing the main fracture treatment design.
This paper describes how minifrac analysis data is used to compute the Nolte G time function (NGTF) and assess fracture pressure decline behavior and evaluate closure pressure and reservoir permeability. The calculated permeability from the minifrac is then compared to the well test pressure data analyses results. Calibration is performed to match the results with well test analyses, which is considered to provide the most precise information about the reservoir. Once a good match is obtained, the process is extended to subsequent wells that allow computing reservoir permeability values using minifrac only, thereby optimizing hydraulic fracture design and predicting production performance.
Source: SPE Middle East Oil & Gas Show and Conference, 8-11 March 2015, Manama, Bahrain
Authors: Zillur Rahim (Saudi Aramco) | Hamoud Al-Anazi (Saudi Aramco) | Dwi Waspada (Saudi Aramco) | Adnan Al-Kannan (Saudi Aramco) | Eduardo Pacheco (Halliburton)