|Publisher||American Rock Mechanics Association||Language||English|
|Content Type||Conference Paper|
|Title||Hydraulic Fracturing Mechanisms In Carbon Sequestration Applications|
|Authors||Johnson, S. M. and Morris, J. P. ; Lawrence Livermore National Laboratory|
|Source||43rd U.S. Rock Mechanics Symposium & 4th U.S. - Canada Rock Mechanics Symposium, June 28 - July 1, 2009 , Asheville, North Carolina|
|Copyright||2009. American Rock Mechanics Association|
Geologic carbon sequestration is becoming an increasingly viable method for reducing the rate of greenhouse gas emissions through the injection of CO2 into geologic reservoirs. To be effective, this technology must be implemented on a large scale; however, several uncertainties remain about the effect of such large rates and volumes on individual reservoirs and whether this may present a failure risk. Hazards such as fault activation through increased pore pressure or creation of new fractures through the injection process remain significant risks for site failure. As part of a larger effort to understand the interrelationships between different failure mechanisms, we will focus here on the role of hydraulic fracturing in reservoir geomechanics. This study will detail efforts using a finite-discrete element code (LDEC) coupled with a 2-D finite volume solver for fluid flow through fractured rock. An overview of the approach will be provided as well as current results of a continuing study into the effects of hydraulic fracturing and fluid flow for a fractured CO2 sequestration site. We will also discuss implications for broader successful implementation of geologic CO2 sequestration.
The sequestration of carbon in geologic reservoirs has garnered increasing interest due to both the increase in global support for reductions in greenhouse gas emissions as well as the potential for the technology to enable a graceful transition between current energy generation technologies and renewable sources. Geologic sequestration is especially compelling as an early adoption solution due to both the geographic dispersion of viable sites, which are often within a reasonable distance of current CO2 sources, as well as the potential for positive revenue streams for operators when used in conjunction with oil, and gas stimulation operations.
One of the risks associated with these sites is the uncertainty of how they will react to a large influx of CO2 when operated at scale. Several failure mechanisms for the reservoir have been theorized, including reactivation of pre-existing fractures to enable transport and tensile failure of the caprock due to the elevated pressure in the reservoir. Here, we attempt to address these two risks through numerical simulation and modeling.
The efforts described here use a finite-distinct element code (LDEC) coupled with a recently developed 2-D finite volume solver for fluid flow through fractured rock . Together, these capabilities allow problems in hydraulically driven fracture to be effectively addressed at moderate spatial and temporal scales using the explicit formulation and at larger and longer scales using the implicit version of the fluid solver. An overview of the model and its range of applicability will be presented as well as the results of verification and validation studies on the combined approach. The current results from an ongoing study of the effects of hydraulic fracturing and fluid flow for a fractured CO2 sequestration site as well as the implications for successful geologic sequestration of CO2 will also be discussed.
There has been an expansive body of research into the modeling of fractures and the specific complications of fracture phenomena in reservoirs.
|File Size||494 KB||8|