Impact of Bedding Planes Orientation on Fracture Propagation in Berea Sandstone Rocks during Hydraulic Fracturing

Abstract

Hydraulic fracturing is an important stimulation method to increase hydrocarbon production from tight reservoir. To the best of our knowledge, there are no systematic laboratory Hydraulic fracturing experimental studies on the effect of bedding planes, which are weak joints within the rock, on Hydraulic fracturing at reservoir conditions. The objective of this research is to investigate the impact of bedding planes orientation under reservoir conditions on the ultimate elastic pressure, fracture initiation pressure, breakdown pressure, and fracture pattern in Berea sandstone experimentally and computationally. A fully coupled mechanical-hydraulic analysis is performed assuming compressible fluid and transient flow using universal distinct element code (UDEC) commercial software. Furthermore, a 3D model without bedding planes was built using Abaqus software and was used to study the elastic principal stresses at injection hole subjected to fracturing. Based on experimental data we propose a new accurate method to determine the initiation pressure, by plotting the cumulative acoustic energy values as function of the injection pressure. The pressure at injection hole function of injection time for all the tested samples follows three distinct shapes and have been classified to three classes. Class-1 is the preferred as it is characterized with high build-up of pressure in the injection hole and low or no leak-off to the fractures, and is dependent on both the bedding planes angle and the injection rate. We show that the ideal injection rate for each bedding plane angle, based on higher breakdown pressure, shorter time, and less injection volume, is 10 cc/min for angles 45° and 60°, and 20 cc/min for angles 0° and 90°. The injection volumes are independent of bedding planes at 0⁰ and 90⁰ when injection rate is 20 cc/min and are independent of bedding planes at 45⁰ and 60⁰ when injection rate is 10 cc/min. There is a correlation between minimum injection volume and ideal injection rate. The injection hole maximum principal stress is always in tension at all injection rate values, while the surrounding outside the injection hole is in compression. It is concluded that the bedding planes of 0° have the lowest maximum principal stress, while 90° have the highest. The computational model reproduced the experimental model. The breakdown pressure in both has the same trend. The computational model underestimates the breakdown pressure for low value bedding planes angle 0˚ to 30 ˚ and overestimates for higher value bedding planes angle 45˚ to 90 ˚. The minimum breakdown pressure from the experimental work and computational work is at bedding planes of 30 ˚, and this in agreement with the literature reviews. For all tested bedding plane angles, the main fracture follows the direction of maximum stress in both simulations and experiments.

Date of Award	Dec 2022
Original language	American English
Supervisor	Rashid Abu Al Rub (Supervisor)