Logging Equipment Applied During Geothermal Well Drilling.docx

1. Logging equipment applied during geothermal well drilling 1) Caliper and cement bond logging - To measure the variation in well diameter and assessing the integrity of casing cementing 2) Geophysical logs - Aimed at estimating different physical properties of rocks intersected by the well. - This type of logging also supplements drill cutting analysis, in particular for depth intervals where drill cuttings aren’t available, e.g. due to total circulation loss. Such logs include various types of resistivity logs, neutronneutron logs aimed at estimating water content (dependent on porosity), gamma-gamma logs aimed at estimating rocks density, sonic logs aimed at estimating seismic wave velocity and natural gamma ray logs, which can be used to distinguish certain types of formations. 3) Televiewer logging - used to study specific fractures and fracture distribution in wells. 4) T & P logging

2. At Completion the main purpose is to assess the result of the drilling operation. T & P logging equipment’s accompanied by spinner logging to evaluate the location and relative importance of feed-zones Geophysical logging and fracture imaging of the production part of the well. Step-rate well-testing; through injection in high-temperature wells or production in low temperature wells. Pressure (and sometimes temperature) transients measured down-hole. 4) Temperature and pressure logging is normally performed after, sometimes even during step-rate testing. Spinner logging can be beneficial to assess feed-zones. 5) Well stimulation equipment 1) 2) 3)

3. During warm up and Production testing 1) 2) 3) 4)

T & P logging Spinner logging – A spinner measures the relative velocity of fluid past the tool. Well discharge measuring equipment Chemical tracers

4. During Reservoir Monitoring 4.1

Main parameters measured

The main purpose is to provide information on the fluid produced and reinjected, and to allow long term monitoring of the physical and chemical changes that occur. Interpretation of this data and reservoir modeling is necessary for understanding the reservoir behavior. In most countries such data must also be sent to a designated government authority at regular intervals. This data is also very valuable to the daily running of the power plant to meet production goals and to detect any abnormality in the well or

its operation that may require human intervention. The main parameters measured are: 1. The wellhead pressure (WHP bar-g) is recorded continuously for each well and in many cases also the wellhead temperature (WHT °C). 2. The total flow rate is measured continuously for each well (Q kg/s), and because of the difficulty of measuring 2-phase flow also the total steam and water flow may be measured. In some cases, the turbine output (MWe) is used to estimate the steam flow as a turbine is quite a good “steam meter”. 3. Down hole temperature and pressure surveys are made 1- 2 times per year, either with the well shut in or while flowing. 4. Observation wells and reinjection wells have the pressure recorded on surface or downhole. 5. Caliper surveys are made of the well casing intermittently, for determination of any change in diameter either from scaling, casing damage or corrosion. For this, baskets of different diameters are run on a wireline into the hole. Special multi-finger casing calipers are sometimes run to detect corrosion damage along with a CCL tool. A multiarm electrical caliper tool can be run into the well when quenched. Some hightemperature calipers are available. 6. Chemical samples are taken at the wellhead 1-2 times per year through a small sample separator of the steam and water phases. 7. Steam samples are taken regularly at the turbine inlet to measure noncondensible gases and selected minerals for determination of steam purity. 8. An output test is made about once a year by diverting the well flow temporarily to a silencer/separator and measuring equipment. Usually the lip-pressure method for total flow and V-notch weir for water flow is used. This allows the well “output curve” to be Thorhallsson 198 IGC2003 – Short Course determined (by measuring mass flow vs. WHP for several points) and for the average fluid enthalpy to be calculated (kJ/kg). Temporary injection of tracers into 2phase pipelines is also used to determine the flow rate of steam and water phases separately by

injection of a volatile (e.g. sulphur hexaflouride SF6 for steam flow) and nonvolatile tracers (e.g. sodium benzoate C7H5O2Na for water flow). This method does not require diversion of the flow or silencer/separator measuring equipment in the field. It does, however, require portable dosing equipment and balances to measure the dosing rate and laboratory equipment for determination of the tracers in the respective phases. 9. On low-temperature wells having down-hole pumps, the motor Amp, Hz (on variable speed pumps), down hole pressure (draw-down) and discharge pressure at the surface is also measured. 10. Corrosion coupons are sometimes installed at the wellhead of production and reinjection wells to monitor the corrosion/scaling situation. It is preferable to use coupon holders that can be inserted and withdrawn without stopping the flow (Figure 5).

Mechanical TP tools Mechanical Amarada and Kuster T and P tools are a well-established part of geothermal logging. The tools were developed early in the last century. They have been in use since the late fifties, in Iceland, and have proven their value. They are still in use today, though moreover for application in extremely demanding situations or simply as back up for more advanced tools. Mechanical tools are well known within the geothermal community and therefore they are only briefly mentioned here. Mechanical tools are one-sensor tools that measure either temperature or pressure. The tools work by a simple array of components, i.e. in order to measure, one need to “load” the tools and set the clock. In short, the steps are: change O-ring, insertion of carbon chart in to the sledge, making a baseline, wind and attach clock (which pushes the sledge down), and enable a needle (scratching the carbon chart with increased T or P). Logging is done by stopping at intervals of 50- 100 m, the T sensor is rather slow in response time and one can expect the reading to be of a duration of 10-15 min. where drastic T changes takes place and never to be less than 5 min. The P sensor is somewhat faster and usually 3-5 min. will allow for a reading. This procedure is clearly rather timeconsuming and the resolution of data points is relatively poor. The resolution does not improve when measuring with time, as for pump tests, and valuable data can be lost.

Electronic TP tools

K10 Geothermal PTS

The K10 Geothermal PTS is a subsurface high temperature tool designed to continuously measure and record downhole temperature, pressure and flow in geothermal wells. The instrument can operate downhole for up to 6 hours at 300°C and 4 hours at 350°C. The electronic section of the instrument is encased in a pressure housing, which thermally protects it from the high geothermal temperatures. The pressure transducer senses wellbore pressure through a capillary tube, while the RTD sensor remains exposed to the wellbore for accurate and fast response temperature sensing and recording. Interchangeable flowmeters and impellers allow you to choose what is best suited for the flow conditions. All materials meet NACE MRO175 specifications for corrosive wellbore media.

K10 Depth Unit The K10 Depth Unit operates with either a K10 Quartz, K10 Strain or K10 Geothermal pressure and temperature gauge. The unit will display and record depth and line speed during a slickline operation. Using its built in Real Time Clock, the unit will automatically record the start date, time and record depth and line speed. This data is then merged with the tool data for depth and line speed correlation.

K10 Surface Readout (SRO) Unit

The K10 Surface Readout (SRO) Unit operates with either a K10 Quartz or K10 Strain pressure and temperature gauge. The unit provides power and receives data from the downhole tool over a single conductor cable. The data is displayed at the Surface Readout System and/or PC. The unit will also record depth and line speed when using a digital encoder.

Flow Through Sampler (FTS) The Küster Flow Through Sampler (FTS) is a device for obtaining fluid samples from a producing well. The sample chamber is lowered into the well with open valves on each end, allowing well fluids to pass freely through the chamber. At an interval programmed on the surface, the valves close, trapping the fluid. The sampler can then be removed from the well. The sample contained in the chamber will remain in the same state as it was in the well. The pressure will not be changed. The sample can then be removed from the sampler and transferred to a container suitable for storage by means of a transfer apparatus. The transfer can be made without changing the pressure of the sample or contaminating it. The instrument consists of a sample chamber with a spring loaded valve on each end. A latching mechanism connects the valves together and holds them open. Above the chamber, there is a clock to program the closing time, and a ball operated tripping mechanism to release the valves. The lower end has a removable bull nose with ports to allow the fluid to enter. At the top, there is a rope socket for attaching the wireline.

KPG Pressure Gauge - KTG Temperature Gauge The bottom-hole pressure measurements of the KPG gauge and the temperature recordings of the KTG gauge are accurate, sensitive, reliable and cost effective. The KPG and the KTG LV Temperature Recorder use the principal of the multiple helical coil bourdon tube, which has been used for over 50 years providing rugged and dependable operation. The KTG Bi-Metal Temperature Recorder uses two unique metals which react differently to temperature. This reaction creates rotation in the coil. The clock is used to regulate the travel of the chart carrier through the lead screw, lead nut and push rods. The recording section of the KTG LV and Bi-Metal transmits the rotation of the bourdon tube (or external coil) to the stylus shaft which is connected to the stylus assembly, rotating within the chart carrier. The stylus assembly scribes a mark on a coated chart within the chart carrier. The LV element uses an external coil on the top end which transfers temperature down through the sensing element. The Bi-Metal element uses a special housing that transfers well temperature to the sensing element. Both the LV and the Bi-Metal elements are quick responding, corrosive resistant and reliable. The KTG temperature gauge includes: temperature element, HP clock, recorder, wireline socket, standard calibration table and instruction manual. The KPG and KTG are also sold separately as a clock, recorder and pressure or temperature element. Kuster Company can customize gauges for your particular application. Also available are: Field Kits, carrying cases, charts, thread lube and spare part kits.

Standard Mud Logging equipment Mud Logging:

Mud logs enable the geological description and analysis of rock cuttings suspended within the returned drilling mud and can provide a variety of useful information regarding reservoir parameters. Mud logging is the analysis of the drilling mud that has been cycled down the borehole and returned to the surface during drilling operations. The drill mud carries rock fragments from the bottom of the borehole and these rock fragments are used to determine the downhole lithology. A mobile laboratory is set up near the drilling rig so that mud logging can give close to real time data of the lithology and borehole fluid during a drilling operation. Mud logging is also important for monitoring the drill fluid volume so the drill operator knows if fluid is being lost to a formation. Mud logging is a standard practice during drilling operations and normally a third party mud logging company is hired to perform the task.

Field Procedure Samples from the drilling mud are taken at predetermined intervals. The samples are taken to the onsite laboratory and the drilling mud is separated from the drill cuttings. The drill cuttings are dried and viewed under a microscope then geologic descriptions are written up describing the lithology of the cuttings. Drill cuttings are often displayed in order of depth they were received from so that the change in lithology relative thickness of strata can be viewed and documented. Equipments Shale shaker

Fluid Sampling -

Obtaining samples of formation fluids (steam and/or liquid) at a specific depth is important for development of a geochemical reservoir model The sequence of methods in this section is:

a) Sampling hot springs, fumaroles, etc. b) Sampling condensed brine and entrained gases.

c) Sampling steam-lines. d) Low pressure separator systems. e) High pressure separator systems. f) Two phase sampling. g) Downhole samplers.

Sampling Equipment: Sample bottle: Two glass, or polyethylene, sample bottles with 15-cm lengths of wide-bore butyl rubber tubing over their necks and with a screw clip placed halfway up the tube are used. Tygon tube: For sampling seeps from hot springs where only a limited amount of fluid is

available. 500 ml Nalgene bottles: used for collecting bottles Naughton tube: for sampling volcanic fumaroles. Two 60 ml polypropylene syringes: for sampling dissolved and entrained gases in fumaroles, hot springs or steam wells Sealable bottle: Sampling silencer weir boxes for liquid. Glass separator: for determining liquid and gas. Evacuated cylinders: Sampling of gas and liquid from wellheads, pipelines, etc. Klyen downhole sampler: Downhole sampling of liquid and gas. Evacuated flask: Sampling of reactive gases (C02 and H2S) from silencers.

Recommended Analytical Methods for Geothermal Liquids The sequence of methods listed for each parameter is: Wet chemical. Gravimetric. Colorimetric. Electrode. Atomic absorption. Flame emission. X-ray fluorescence. Inductively coupled plasma-atomic emission spectroscopy Ion exchange chromatography. Spark source mass spectrometry. Neutron activation analysis.

Emission spectrometry.