Mathematical modeling of geomechanical behavior of tarmat during the depletion of giant oil reservoir-aquifer systems

Ayse Pamir Cirdi,Luis F Ayala H,Ali H Dogru,Turgay Ertekin

doi:10.1007/s13202-011-0008-4

Abstract

In this work, deformation and failure behavior of tarmat layers during depletion of a giant reservoir–aquifer system has been studied. Deformation response of the tarmat to increasing pressure differential caused by continuous depletion of reservoir is examined and a mathematical model is developed for the study of this type of composite systems. The geomechanical failure that takes place when the pressure differential reaches a critical value is also evaluated, along with the characterization of the resulting fracture. Plate theory, maximum shear stress failure criterion, conventional well test model, Perkins–Kern–Nordgren (PKN) and Khristianovic–Geertsma–de Klerk (KGD) models and flow through fractures models are used. The developed sensitivity analysis proposes the proper protocol to be followed in order to undertake production design in such composite systems. The methodology presented in this paper, ultimately, predicts fracture width and fracture permeability that would be developed in a system with a tarmat layer having a certain thickness and a reservoir being produced at a certain production rate and total depletion time.

Highlights

Oil resources are located in various types of reservoir formations, varying with properties, dimensions andJ Petrol Explor Prod Technol (2011) 1:71–80 part of the analysis involves the characterization of the fracture and its permeability and the resulting communication between the aquifer/reservoir system.Tarmat deformation analysisThis study focuses on a three-layered composite system, typical of giant oil fields in the Middle East
The methodology presented in this paper, predicts fracture width and fracture permeability that would be developed in a system with a tarmat layer having a certain thickness and a reservoir being produced at a certain production rate and total depletion time
Deformation versus loading behavior is investigated until the point where maximum shear stress failure criterion predicts geomechanical failure

Summary

Introduction

J Petrol Explor Prod Technol (2011) 1:71–80 part of the analysis involves the characterization of the fracture and its permeability and the resulting communication between the aquifer/reservoir system. This study focuses on a three-layered composite system, typical of giant oil fields in the Middle East. Upper layer contains mobile reservoir fluids, middle layer is referred as the tarmat, and the bottom layer is a high pressure water aquifer. Tarmat is an extremely viscous hydrocarbon layer, mainly composed of tar or bitumen, which exists between oil and water contact. The tarmat acts as a permeability barrier between the reservoir and its aquifer.

Objectives

Results

Conclusion