Drilling Consultancy, Well Logging, Testing and Evaluation

Iceland GeoSurvey has extensive experience assessing all surveys and results from previous drilling to advise the customer on drilling location and drilling program.  The company further provides well testing, a key aspect in exploration and production drilling, well maintenance, and geothermal field management services.

Drilling Consultancy

Iceland GeoSurvey can provide drilling consultants, well site geologists, logging experts and tools for down-hole measurements during drilling. In addition to the standard geothermal drilling consultancy and well site support, Iceland GeoSurvey provides expertise in overcoming drilling problems.

The findings are presented in a comprehensive Drilling Report. Various tests are made at the end of drilling to assess the outcome. All information is presented in such a way that it can later be used for integrated studies and conceptual modeling.

Iceland GeoSurvey offers full scale drilling services on the following items:

• Selection of well site and description of the well target – This is based on various surface exploration data.
• Design of drilling programs – Advice is provided on the most appropriate drilling technology to be applied and ways to overcome drilling problems. Description of the expected drilling conditionins is provided including specification on the casing program, drilling fluids, cementing, measurements to be carried out etc.
• Mud logging and onsite geological consulting – Well site geologists carry out binocular and microscopic analysis of the cuttings and identify the alteration minerals. The downhole stratification, intrusions, geothermal alteration and geological relations of aquifers are mapped. Lithological- and alteration logs are prepared together with a plot of drilling information from the rig. First analyses and interpretation of these data are carried out on site for preliminary estimation on formation temperature and structure. Daily reports are issued.
• Well logging and well orientation measurements – Iceland GeoSurvey has a full line of geophysical logging instruments and the trucks and tools to deploy them. These logs do not only give information on the permeable structures and general conditions in the well but are also used in the elucidation of the stratigraphy, alteration, and intrusion history of the reservoir. These tools are run into the hole at casing points to log each section of the well as it is drilled, taking advantage of the temporary cooling of the well by the drilling mud. Additional measurements are made to solve drilling problems. Gyroscopic surveys that are carried out to steer the directional drilling and later to confirm the well track are a special class of measurements.
• Well injection test and stimulation – At the end of the drilling, it is recommended to perform a short injection test to find out how permeable the openings in the well are. Iceland GeoSurvey offers consulting on the design of this injection test as well as recommendations on how to carry out a stimulation program if necessary.
  That could for example include thermal cracking, hydrofracturing and acidising .

Well Logging

Iceland GeoSurvey provides a wide range of open and cased hole logging services, using highly specialized equipment especially suited for the geothermal sector in accordance to the ISO 9001 standard. Iceland GeoSurvey has a long tradition and experience of working in geothermal fields all over the world, and well trained and experienced personnel in logging operations and consultancy.

Iceland GeoSurvey’s objectives are to provide geothermal logging services that enable a better understanding of subsurface conditions in geothermal systems, and provide information for field analysis in regards to:

• Geological subsurface structures of geothermal fields
• Extents and scale of the geothermal reservoirs
• Reservoir monitoring and production forecasting
• Chemical, physical and structural properties of reservoir rocks
• Chemical and physical properties of reservoir fluids
• Chemical and physical processes within geothermal field systems

ISOR maintains three specially equipped trucks for real-time logging in open and cased wells, and another three units for slick-line logging with memory tools. The logging operations are divided into two main temperature categories for well logging below 150°C and above 150°C.

Further details see fact sheet for Well Logging Services linked to below.

Well testing and evaluation

Geothermal well testing involves an array of measurements aimed at gathering information on well characteristics, production potential, and reservoir properties. Stimulation of wells for the purpose of enhancing their output also falls within this category.

Iceland GeoSurvey employs a number of geophysicists, chemists, reservoir physicists, engi- neers, and technicians with long experience in all aspects of geothermal well testing and evalu- ation. These specialists have conducted such work in nearly all drilled geothermal fields in Ice- land, and they have been involved in well testing and evaluation projects worldwide.

Iceland GeoSurvey owns and operates logging trucks and a multitude of logging tools for wireline and electrical logging. Iceland GeoSurvey also runs a chemical laboratory.

Iceland GeoSurvey offers geothermal well testing and evaluation services as follows:

• Temperature and pressure logging – Well logging is used to determine the physical state of a reservoir, to locate feed-zones, and to determine general well conditions. The logging can be carried out either with the well flowing or shut-in.
• Well test design – Iceland GeoSurvey staff design and execute well tests and perform associated pressure transient analyses. This involves single-well tests, including flow tests, injection tests, and recovery tests, and also multi-well tests, such as interference tests. Their purpose is to determine reservoir properties and well characteristics.
• Well stimulation – Well stimulation serves to improve the productivity and injectivity of geothermal wells. The stimulation involves cold water injection, thermal cycling, airlift, and chemical treatment. All these methods aim at opening up and cleaning out existing fractures, and forming new ones. Downhole packers are commonly used to stimulate low-temperature wells.
• Tracer tests – Tracer tests are conducted to delineate connections between different wells, in particular between reinjection and production wells, and to study flow paths in geothermal systems. They are most often used to determine the feasibility of proposed long-term reinjection schemes in resource management.
• Evaluation of wells – The physical, chemical, and mechanical characteristics of the wells are evaluated. The integrity of the wells is verified to ensure their safe operation.