Paper Information

Journal:   PETROLEUM RESEARCH   WINTER 2016 , Volume 25 , Number 85-2; Page(s) 43 To 53.
 
Paper: 

SEMI-ANALYTICAL SIMULATION OF PHYSICOCHEMICAL INTERACTION FOR REACTIVE SHALES

 
 
Author(s):  MIRABBASI SEYED MORTEZA, AMERI MOHAMMAD JAVAD*
 
* DEPARTMENT OF PETROLEUM ENGINEERING, AMIEKABIR UNIVERSITY OF TECHNOLOGY, TEHRAN, IRAN
 
Abstract: 

Shale formation instability is the main source of many problems in drilling operation causing significant costs and wasting time. Prior to drilling, mechanical stresses are less than fracture resistance of rock and chemical conditions are in balance within the formation. Because of that, in this balanced situation, the formation is stable. However, shear, tensile and compressive forces vary around the wellbore after drilling operations. Under these conditions, the rocks around the well become unstable. On the other hand, while the formation contacts with drilling fluid, chemical interactions occur, one of possible reasons for the wellbore instability. Hydraulic pressure transmission and osmotic pressure are the main mechanisms of shale formation instability. Thus it is very vital to delay the pore pressure increase surrounding the well. This can be achieved by adding various salts and applying different types of nano-particles or polymers to block the shale pores to improve the shale membrane properties. In order to prevent consequential problems associated with shale formations, it is necessary to study the formation characteristics and evaluate changes occurred due to rock-fluid interaction. Hence, in this paper, the field equations governing the problem have been derived based on the linear chemo-poroelastic theory. Since Diffusion equations are mainly fully coupled, therefore by using analytical/ numerical methods, these equations have been decoupled and solved finally. The simulation results show that the proposed model can appropriately simulate the pore pressure transmission test (PPTT) and shale formation behavior contact with drilling fluid.

 
Keyword(s): SHALE FORMATION INSTABILITY, OSMOTIC PRESSURE, SHALE MEMBRANE EFFICIENCY, CHEMO, POROELASTIC THEORY, ANALYTICAL, NUMERICAL METHODS
 
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