| Title | Geological Approach to Successful Geothermal Well Drilling |
|---|---|
| Authors | Ronald 0. Vicedo, Releo Roel D. Contemplacion, Armando C. Licup, Jr., Winston V. Freires, Edwin B. Herras |
| Year | 1996 |
| Conference | PNOC-EDC Geothermal Conference |
| Keywords | |
| Abstract | Geothermal wells of PNOC-EDC target subsurface faults as the main source of permeability in the open hole. This is a consequence of having very limited to nil primary permabilities in the thick volcano sedimentary deposits and intrusive bodies underlying most geothermal systems being developed by the company. This lack of specific permeable horizons in the subsurface from which fluid can be extracted necessitate that geologists make use of all data available to them in identifying possible fault intercepts in wells to be targeted by drilling. For a well targeting a fault with a still unestablished subsurface dip range, close monitoring of the cuttings and drilling parameters can greatly help pinpoint likely fault intersections as drilling proceeds. In the case of several wells having drilled through a common fault on the other hand, enough geological data supported in part by drilling and well test information can be correlated to come up with a specific dip range representative of the fault k main dip value. The dip range arrived at can then be used to make a reliable projection on when a new well will intersect a fault based on its programmed profile. Two wells drilled in LGPP were chosen to exemplify how these procedures help geologists in identifying subsurface permeable faults whose intersections dictate the degree of success of drilling. WellsMG-9D and 4R4D > re-entry were chosen due to the methods by which their intercepts with a specific fault were identified, one during actual drilling phase where problems related to a geological structure were successfully addressed, and the other prior to drilling in an attempt to locate additional targets to improve the very limited capacity recorded a per completion of the well. In both cases, the procedures used in identifying their respective target faults proved their effectiveness which led to the successful attainment of the objectives for drilling. |