Identifying Fracture Types and Relative Ages Using Fluid Inclusion Stratigraphy

Dilley, Lorie M. ; Norman, David ; Owens, Lara

关键词: FRACTURES;    GAS ANALYSIS;    GASES;    GEOTHERMAL SYSTEMS;    HYPOTHESIS;    LIFE CYCLE;    STIMULATION;    STRATIGRAPHY;    TARGETS;    WELL DRILLING;    WELL LOGGING Enhanced Geothermal Systems;    Fractures;    Fluid Inclusion Stratigraphy;   

DOI  :  10.2172/933170
RP-ID  :  DOE GO16057-1
PID  :  OSTI ID: 933170
Others  :  Other: HDL 06-301
Others  :  TRN: US200818%%718

学科分类：再生能源与代替技术

美国|英语

来源: SciTech Connect

【 摘 要 】

Enhanced Geothermal Systems (EGS) are designed to recover heat from the subsurface by mechanically creating fractures in subsurface rocks. Understanding the life cycle of a fracture in a geothermal system is fundamental to the development of techniques for creating fractures. Recognizing the stage of a fracture, whether it is currently open and transmitting fluids; if it recently has closed; or if it is an ancient fracture would assist in targeting areas for further fracture stimulation. Identifying dense fracture areas as well as large open fractures from small fracture systems will also assist in fracture stimulation selection. Geothermal systems are constantly generating fractures, and fluids and gases passing through rocks in these systems leave small fluid and gas samples trapped in healed microfractures. Fluid inclusions trapped in minerals as the fractures heal are characteristic of the fluids that formed them, and this signature can be seen in fluid inclusion gas analysis. Our hypothesis is that fractures over their life cycle have different chemical signatures that we can see in fluid inclusion gas analysis and by using the new method of fluid inclusion stratigraphy (FIS) the different stages of fractures, along with an estimate of fracture size can be identified during the well drilling process. We have shown with this study that it is possible to identify fracture locations using FIS and that different fractures have different chemical signatures however that signature is somewhat dependent upon rock type. Open, active fractures correlate with increase concentrations of CO2, N2, Ar, and to a lesser extent H2O. These fractures would be targets for further enhancement. The usefulness of this method is that it is low cost alternative to current well logging techniques and can be done as a well is being drilled.