Production Wells

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Exploration Technique: Production Wells

Exploration Technique Information
Exploration Group: Drilling Techniques
Exploration Sub Group: Development Drilling
Parent Exploration Technique: Development Drilling
Information Provided by Technique
Lithology: Drill cuttings are analyzed to determine lithology and mineralogy
Stratigraphic/Structural: Fractures, faults, and geologic formations that the well passes through are identified and mapped.
Hydrological: Identify aquifers, reservoir boundaries, flow rates, fluid pressure, and chemistry
Thermal: Direct temperature measurements from within the reservoir
Dictionary.png
Production Wells:
A well drilled with the primary purpose of bringing geothermal water and steam to the surface for commercial utilization.
Other definitions:Wikipedia Reegle


 
Introduction
A production wells primary purpose is to bring geothermal fluids to the surface for commercial utilization. Production wells are normally larger in diameter and deeper than exploratory wells, thus they are also much more expensive to drill. Drilling of production wells are the last step in the exploration process and developers normally have a good reservoir model established from other exploration methods before production drilling takes place. Production well designs can vary greatly depending on target depth, expected down hole conditions, and drilling equipment available. Production well drilling can be very complicating and often costs around 1-7 million dollars per well.[1]

Cost increases with depth drilled and time spent drilling. Estimating drilling times and costs is extremely difficult because there are many different well designs and many unknown factors that will influence the drilling operations such as loss of drilling fluid, drilling rates, and number of drill bit changes just to name a few.[2]

Drilling costs as a function of well depth, comparing geothermal wells (red line) to oil and gas wells (black line). Drilling costs increase exponentially with depth.[3]

 
Use in Geothermal Exploration
Production wells are essential for geothermal utilization and are the link between a geothermal reservoir and the surface. The main goal of a production well is to reach areas within the reservoir that have the highest permeability, temperature, and pressure, so that the highest enthalpy fluids can be extracted. A production wells main purpose is geothermal utilization but they can also be considered an exploration method because data from the first production well will often lead to a better drilling location for a second production well. Production wells are the best means for acquiring direct measurements from within the reservoir and the information gained from each successive production well enhances the reservoir model allowing for improvement in each drilling effort. Due to the high costs, drilling production wells is the most risky step in geothermal development. Drilling costs will normally consist of about 35-40% of the total capital cost during a geothermal project.[1] Not all production wells will be successful but on average a strong production wells can often provide enough geothermal fluids to generate around 5-7 MW of electricity. Most wells drilled throughout the world produce 3 MW.[1] On average the success rate of the first production well drilled in a geothermal area is about 50%.[1]
 
Related Techniques

 
Field Procedures
Drilling of production wells requires the largest type of drill rigs, large quantities of material, and a high amount of water. Once the drilling location is established the land needs to be cleared to make way for the drilling rig and all of the associated equipment. In remote areas access roads may need to be constructed. There are many types of drilling procedures and well designs that can be used depending on the geology, target depth, expected temperatures, flow rates, etc. for a detailed description of geothermal drilling methods see chapter 6 (Drilling and Well Construction) in Geothermal Direct Use Engineering and Design Guidebook.[2]

Geothermal drilling at Te Mihi west of Wairakei, New Zealand.[4]

 
Environmental Mitigation Measures
When multiple wells are to be drilled sometimes direction drilling can be utilized so that more than one well can be drilled from the same drilling pad. This reduces land usage by reducing the amount of drilling pads, the amount of access roads needed, and the amount of pipeline tracks needed.



 
Best Practices
Firm evidence from multiple exploration techniques is very important when deciding where to drill production wells. A solid reservoir model should be in place when deciding on the best drilling locations.
 
Potential Pitfalls
Production wells are very expensive, so an unsuccessful well can be very costly to the company.








 
References
  1. 1.0 1.1 1.2 1.3 International Finance Corporation, GeothermEx Inc.. 2013. Success of Geothermal Wells: A Global Study. Washington, D.C.: International Finance Corporation.
  2. 2.0 2.1 Gene Culver. 1998. Geothermal Direct Use Engineering and Design Guidebook - Chapter 6 - Drilling and Well Construction. N/A: Geo-Heat Center. 129-164p.
  3. Jeff Tester. 2011. Oil and Gas Well Drilling. N/A. N/A. Oil and Gas Well Drilling; N/Ap.
  4. Geothermal drilling at Te Mihi NZ.jpg [Internet]. 2010. Wikimedia Commons. [cited 2013/10/03]. Available from: http://commons.wikimedia.org/wiki/File:Geothermal_drilling_at_Te_Mihi_NZ.jpg



    Document # Analysis
    Type
    Applicant Geothermal
    Area
    Lead
    Agency
    District
    Office
    Field
    Office
    Mineral
    Manager
    Surface
    Manager
    Development
    Phase(s)
    Techniques
    DOI-BLM-CA-670-2010-107 CX Ormat Nevada, Inc. North Brawley Geothermal Area BLM BLM California Desert District Office BLM BLM Geothermal/Well Field Production Wells
    DOI-BLM-NV-063-EA08-091 EA Ormat Technologies Inc Buffalo Valley Hot Springs Geothermal Area Bureau of Land Management BLM Battle Mountain District Office Bureau of Land Management Bureau of Land Management Geothermal/Power Plant Production Wells
    DOI-BLM-NV-B010-2011-0015-EA EA Ormat Technologies Inc McGuinness Hills Geothermal Area Bureau of Land Management BLM Battle Mountain District Office Bureau of Land Management Bureau of Land Management Geothermal/Power Plant Drilling Techniques
    Well Testing Techniques
    Production Wells
    DOI-BLM-NV-C010-2009-0018-EA EA Magma Energy Soda Lake Geothermal Area Bureau of Land Management BLM Carson City District Office BLM Stillwater Field Office BLM Bureau of Reclamation Geothermal/Well Field Production Wells
    DOI-BLM-NV-C010-2012-0016-DNA DNA Ormat Technologies Inc Salt Wells Geothermal Area Bureau of Land Management BLM Carson City District Office BLM Stillwater Field Office Bureau of Land Management Bureau of Land Management Geothermal/Well Field Production Wells
    DOI-BLM-NV-C010-2013-0020-DNA DNA Gradient Resources Geothermal Drilling Permit Application Well 14-28 Patua Geothermal Area Bureau of Land Management BLM Carson City District Office BLM Stillwater Field Office BLM Bureau of Reclamation Geothermal/Well Field Production Wells
    DOI-BLM-NV-C010-2013-0026-DNA DNA TGP Coyote Canyon LLC Dixie Valley Geothermal Area BLM BLM Carson City District Office BLM Stillwater Field Office BLM BLM Geothermal/Well Field Production Wells
    DOI-BLM-NV-CO10-2011-0501-EA EA Gradient Resources Patua Geothermal Area Bureau of Land Management BLM Carson City District Office BLM Stillwater Field Office BLM Geothermal/Well Field Thermal Gradient Holes
    Production Wells
    NEPA Process for Geothermal Power Plants in the Deschutes National Forest EIS Cal Energy Newberry Caldera Geothermal Area USFS
    BLM
    Geothermal/Exploration
    Geothermal/Well Field
    Geothermal/Power Plant
    Exploration Drilling
    Exploratory Boreholes
    Production Wells
    Thermal Gradient Holes
    San Emido Geothermal Energy North Project EA USG Nevada LLC San Emidio Desert Geothermal Area BLM BLM Winnemucca District Office BLM BLM Geothermal/Power Plant
    Geothermal/Well Field
    Production Wells


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