Loading...

Numerical Evaluation of the Influence of Hydro-Mechanical Factors on the Conventional Methods of Hydraulic Fracture Analysis in Oil Reservoirs

Saligheh Doust, Mostafa | 2019

730 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52397 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. The exploitation of oil and gas has been changed dramatically since the advent of hydraulic fracturing. Hydraulic fracture is one of the enhanced oil recovery methods in which high-pressure injecting fluid is pumped into the well to overcome the lowest in-situ stress and rock resistance to create cracks in the deep-rock formations. It is estimated that the benefits of the mentioned method lead to a net economic profit of $48 billion per year in the world’s oil and gas industry.While there are various analytical models for predicting hydraulic fracture characteristics, KGD and PKN are amongst the most popular Models. The conditions of plane strain in two-dimensional space are taken into account in both models with two different approaches (one in the horizontal plane and the other in the vertical plane). The purpose of this research is to study the effects of the different parameters on hydraulic fracture operation by numerical modeling and compare the results with two analytical models’ results, namely KGD and PKN. Despite having much simplification, analytical models play an essential role in two aspects: first, they are the criteria for validation of numerical simulations. Second, an analytical model, as long as it is formulated carefully, it is an ideal tool for investigating the effect of different parameters on the problem.Some of the practical factors in this process are considered in these Analytical models (such as modulus of elasticity and Poisson's ratio of rock, injection rate, and injection time). However, some other factors (in-situ stresses, Leak-off, permeability of filter-cake, pore pressure) have not yet been considered in these models. In the present study, the effects of overlooked parameters in the mentioned analytical models have been investigated with Abaqus using XFEM. In this study, it has been shown that minimum in-situ stress, tensile strength of reservoir rock, amount of leak-off, pore pressure, and application of poroelastic medium (Biot-coefficient), depending on conditions, have different and significant effects on Hydraulic fracture characteristic. Also, to enhance the accuracy of the KGD and PKN’s equations for estimating the crack properties in the presence of in-situ stress, correction factors have been proposed. Dismissing these parameters and their effects on hydraulic fraction operation can lead to inaccurate estimation of crack properties and, consequently, the failure of the process.Deep in the earth, the influence of rock's tensile strength is negligible, and the minimum in-situ stress is the predominant parameter, which leads to a reduction in the crack's length and an increase in the crack's opening pressure. Extreme in-situ pressures can even prevent the crack from elongation. Fluid leak-off into the formation, except for very low permeable formations, reduces the crack's length and width. Applying poroelastic medium formulation into the low permeable formations leads to a reduction in the crack's length up to 15%. Considering the pore pressure in the formation will increase the crack opening pressure as much as the amount of pore pressure of the formation, while the length and width of the crack will not change
  9. Keywords:
  10. Hydraulic Fracturing ; Poroelastic Medium ; Hydromechanical Factors ; Extended Finite Element Method ; In-Situ Stresses ; Filter Cake ; Leak-Off

 Digital Object List

 Bookmark

No TOC