GRC Transactions, Vol. 43, 2019 
             
             Successful Geothermal Operation Management: Technology 
                      Adoption of Oil and Gas Drilling Rig Systems  
             
                            1               1                   2                    2
                Opeyemi Bello , Catalin Teodoriu , Ogunlana Oluwafemi  and Olatunji Olayiwola  
              1Mewbourne School of Petroleum and Geological Engineering, University of Oklahoma, 
                                                 USA 
                         2Institute of Petroleum Engineering, TU Clausthal, Germany  
             
            Keywords 
            Oil and Gas, rig selection, technology transfer, drilling performance, geothermal development,  
                                              ABSTRACT 
            The development of any oil, gas, or geothermal well is capital intensive, and a substantial part of 
            the cost is related to the drilling. In a recent project report of a geothermal drilling operation in 
            Germany, 36% of the project operational cost is allocated to the drilling rig. As geothermal well 
            drilling is very comparable to oil and gas drilling, with the same principle of rotary drilling rig 
            turning the bit. This signifies that proper drilling rig selection in any drilling operational activity 
            is very decisive, playing a vital role in the design of a cost-effective drilling program for 
            geothermal wells. A wrong choice can lead to downtime, drilling performance and economical 
            effect in terms of unnecessary operation cost. 
            The Oil and Gas drilling industry is a technology dependent industry, leveraging on the emerging 
            technologies in robotics and automation have played a strategic role for operational success in 
            today’s modern rigs system by saving costs, time saving, and increasing safety, improving 
            operating efficiency and solving many optimization problems. Newer and compact rigs are 
            designed to be more productive, provide more reliable uptime, meeting new safety requirements 
            and have a lot more built-in safety features than older rigs. 
            An effective technology transfer and tapping into some of these successfully applied 
            technologies in oil and gas industry will contribute positively to geothermal development, most 
            especially drilling performance by eliminating incidents, increase productivity, minimize 
            downtime and costs and optimize operational efficiency. 
            In this study, we first review the existing drilling rigs for geothermal applications with 
            technology comparisons of the rig systems to oil and gas drill rigs. The influence of transfer in 
            terms of drilling performance, increasing operational efficiency while keeping high safety 
            standards were investigated and summarized. The paper further describes some of the currently 
            tapped in and emerging technologies in oil and gas drilling operations that could benefit 
            geothermal drilling operations. This includes robotics, IoT, drones, data analytics, artificial 
                                                       Bello et al. 
        intelligence and other hardware and software tools allowing to make faster and better decisions, 
        eliminating human error, reduce costs and increase productivity and revenue. 
        1. Introduction 
        Geothermal energy, being derived from the earth's magnetic heat as a source of electricity or to 
        heat cool building; is one of mankind’s major global resources playing an enormous potential 
        effect in many industrial and developing countries through predominately mature technology 
        (Bello et al., 2013). Studied shows that geothermal energy systems have a modest environmental 
        footprint with a potential to become the world’s lowest cost source of sustainable thermal fuel 
        for near-zero emission, base-load direct use, and power generation (Lukawski M.Z., et al, 2018). 
        However, wells that are drilled to tap geothermal energy differ from the much more numerous oil 
        and gas wells. Geothermal wells are usually hotter and are often drilled in harder rocks. There 
        are currently six recognized geothermal resources, namely: hot dry rock (HDR), hydrothermal, 
        magma, EGS, waste heat and geo-pressured. Figure 1shows the geothermal electricity generation 
        capacity be country and the estimated distribution of global growth heat flow in milliwatts per 
        square meter (mW/m²).  
                                                              
        Figure 1: Geothermal electric installed capacity by country in 2015. This figure also illustrates global average 
           heat flow in  milliwatts per square meter and tectonic plate boundaries  (black lines). (Reference 
           Lukawski M.Z., et al, 2018) 
        Drilling  rig selection is one the major bottom line during the development phases  of  both 
        hydrocarbons and geothermal wells, based on comprehensive consideration of a variety of 
        influences for its purpose. Both operations are highly cost intensive as it involves the services of 
        personnel and array of machinery and materials for the duration of drilling the well. Report 
                                                             
         
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      mentioned that geothermal projects tend to be more expensive than oil and gas drilling by 23% to 
      40% for a given depth (Lukawski et al., 2014). 
      The problem of drilling rig performance and selection has always been viewed as the most 
      important responsibility during the well design phase of a field development (hydrocarbon or 
      geothermal wells. The general conception of drilling rig performance used in the geothermal 
      application has been associated with a rig size, mechanical capability, drilling rigs size, 
      mechanical condition, horsepower rating and maximum load. Most of the criteria used for the rig 
      selection are derived from well parameters; especially borehole diameter, depth and casing 
      design. The planning and designing of the well will establish the borehole diameter, which is the 
      principal criterion for whether the well is considered a slim hole or a conventional well. 
      However, in geothermal applications, a large diameter is required; thus, a conventional rotary rig 
      will be a good candidate.  The foremost difference amid conventional hydrocarbon and 
      geothermal drilling is the characteristics of the source rock.  
      Adams (1985) stated that many existing companies most especially operators are applying more 
      effort in rig selection since it is important for the safety, efficiency, and cost of the well. Griffin 
      (2010) also stated that drilling rigs that lead the industry in performance and safely at minimum 
      cost are what drilling owners or operators strive to have, as these rigs will work in many different 
      markets. Thus, with oil and gas drilling industry edging on technological progress, some of these 
      mentioned key performance indicators could be met by reaching the well depth in a safe and 
      controlled manner.  
      The oil and gas drilling industry is a technology dependent industry. Tremendous technological 
      progression has been made in the development and enhancement of both conventional and 
      unconventional rigs for the hydrocarbon development, for example in onshore applications. 
      Advances in technologies have enabled the industry to reach new sources for oil and gas, saving 
      costs, increasing safety, improving operational efficiency and reducing the environmental impact 
      during the drilling operation.  
      Although conventional and improved conventional drilling rig types have been mostly used for 
      different operations over the years, the unconventional over the years has rapidly gained the trust 
      of most operators and well designers. With the recent adaption of technology as a form of 
      automation which has shown proven advantages, newer and compact rigs are designed to be 
      more productive, provide more reliable uptime, meeting new safety requirements and have a lot 
      more built-in safety features than older rigs. Thus, adopting some of these newer and compacted 
      unconventional drilling rigs will play a strategic role in the operational success of geothermal 
      development.  
      This paper summarizes the existing drilling rigs for geothermal applications with technology 
      comparisons of the rig systems to oil and gas drill rigs. The influence of transfer in terms of 
      drilling performance, increasing operational efficiency while keeping high safety standards were 
      also investigated. The study furthermore highlighted some of the currently tapped in and 
      emerging technologies in oil and gas drilling operations that could benefit geothermal drilling 
      operations allowing to make faster and better decisions, eliminating human error, reduce costs 
      and increase productivity and revenue. 
       
                                              
       
                                         Bello et al. 
      2. Oil and Gas Drilling Rig Systems  
      A rotary drilling rig can also be classified into three types: the conventional (traditional) or 
      conventional, improved type and unconventional type. Teodoriu and Falcone (2008) defined the 
      traditional drilling rigs as any type of that is being designed in accord with established forms and 
      conventions with low load capacity with high structure. The improved conventional type allows 
      high load capacity, high mechanization and increased safety. Unconventional drilling rigs are 
      defined as any type of rig that is not conforming to state-of-the-art conventional systems. Most of 
      the current unconventional drilling rigs in the market are characterized mainly by new designs 
      for their hoisting systems to allow very high load capacity within small structures. Other 
      important features of these rigs include electrical hydraulic drives; ability to use the AC electrical 
      supply from a city power grid; low height (single derrick); high load capacity; partially or fully 
      automated control systems, and modular construction.  
      Generally, conventional drilling techniques for geothermal development are applied as long as 
      the drilling process has not yet entered the production zone. For drilling into and through 
      crystalline petrothermal (i.e hot dry rock or enhance geothermal reservoirs) reservoirs, studies 
      recommended using adapted applications for geothermal well drilling. Geothermal drilling rig 
      requirements are very much like those for oil and gas drilling, in terms of design and operational 
      procedures. Conversely, geothermal drilling poses some specific requirements for the selection 
      of a drilling rig: drilling depth (EGS are generally below 5000 m), max hook load (needed for 
      casing running), higher substructure (needed for the BOP stack), mud capacity and cooling. 
      Where EGS wells are concerned, everything rises because of larger well and casing size, deeper 
      drilling targets (5000 m) and hard rock drilling which require intensive tripping; therefore, rigs 
      need to be taller. As drilling rate decreases, the wellbore size becomes smaller or the bit runs 
      decrease as less rotary torque and pump power is desired. The main point at these conditions is 
      on hoisting power to reduce or manipulate the overall tripping time. In application of casing 
      drilling or managed pressure drilling to geothermal development, the load handling capability of 
      the derrick and the top drive is of critical concern. Thus, running the casing deep limits the static 
      depth ranging of the derrick. For managed pressure drilling, the height of the substructure must 
      accommodate a tall BOP stack. 
      In order to make the geothermal projects more compatible using oil and gas drilling systems and 
      increase public acceptance, new compact rig designs take into account the following criteria to 
      makes them environmentally friendly; modular construction, smart power supply, small 
      footprint, and technology sophistication entailing low noise emission hydraulically driven rig, 
      automated control systems, monitoring units, soundproofed housing system, iron roughneck, 
      pipe handling system (PHS) and skidding system with gains in customer specific solutions, 
      safety and efficiency.  
      Summarized below are selected types of drilling rig for oil and gas operations based on the 
      aforementioned three classifications that can be adapted to geothermal well development.  
      2.1 Unconventional Drilling Rigs  
      2.1.1 Herrenknect Terra Invader 350 (Innova Rig)  
      The TI-350 ‘box-on-box’ high tech drilling rig is capable of reaching geothermal resources at 
      depths of 2500 m to 5000 m. The height of the derrick is 52 m with a hook load capacity of 350