The combination of horizontal wells and multistage fracturing enabled the development of tight carbonate reservoirs. The successful completion of these reservoirs can be challenging. Correct placement of multistage intervals plays a critical role in improving and sustaining production. Openhole (OH) multistage (MS) technologies enhances reservoir contact and productivity by optimizing the distribution of the stages across the openhole. This paper presents an engineering technique to optimize OH fracture stages and cluster placement distribution within heterogeneous unconventional oil carbonate reservoirs based on formation, completion properties, and reservoir fluid distribution.
Completion technology is based on distributing intelligent packers along the lateral section to develop the MS fracturing stages. Intelligent packer displacement influences fracture effectiveness and conductivity. Equal spacing packer placement can undermine formation potential and productivity results. The placement of the packers and their ports is based on the petrophysical and mechanical properties of the formation to increase the cumulative production in a shorter timeframe and to help improve recovery. The method followed is based on an analysis of the reservoir properties (porosity and permeability). These were later integrated with the measured rock mechanical properties. The developed integrated model was used to categorize the rock into segments that share similar properties.
The use of an advanced azimuthal sonic tool with a high signal-to-noise ratio and wider frequency response helped to improve the accuracy in assessing formation mechanical properties. In addition, conventional logs, when combined with formation mobility measurements, help to calibrate the permeability model and classify the formation into distinctive clusters. These clusters are then grouped according to their mechanical and brittleness properties to form a separate unit with a selected fracture port to help ensure the necessary fracture length. The developed method provides an opportunity to determine the necessary fracture stages and to reduce the risks of overor underplacement. It also improves stage integrity, helps to ensure better distribution of the acid across the formation matrix, and provides effective propagation of the fracture network.
The applied procedure follows an innovative approach to optimize the fracture stage and cluster placement distribution across the reservoir using a new combination of advanced and conventional data acquisition and interpretation. The case study presented in this paper demonstrates the benefits of engineered fracturing stage placement, as compared to a geometric displacement.