Log acquisition and processing
- 1. LOG ACQUISITION AND PROCESSING
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- 9. LOG ACQUISITION AND PROCESSING Wireline Drilling
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- 11. LOG ACQUISITION AND PROCESSING Measurement While Drilling (MWD) Is a term used to describe drilling related measurements made at the surface or made downhole and transmitted to the surface while drilling a well. MWD as obtaining information about the progress of the drilling operation (rate of penetration, weight on bit, wellbore trajectory, etc). MWD today often refers to geosteering measurements made to help decide on changes to the wellbore path. Measurement-While-Drilling (MWD) specifically refers to information used to help in steering the drill, such as direction, orientation and drill bit information. Measurement While Drilling tools are part of bottom hole assembly (BHA), Gamma ray, directional survey, tool face, borehole pressure, temperature, vibration, shock, torque etc. Results are transmitted digitally to the mud pulser telemetry.
- 12. LOG ACQUISITION AND PROCESSING LWD
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- 14. LOG ACQUISITION AND PROCESSING Logging While Drilling or LWD is the general term we use to describe the systems and techniques for gathering downhole data while drilling a well. LWD is the process of obtaining information about the rocks (porosity, resistivity, etc Drillers and engineers are able to use LWD information immediately to define well placement and predict drilling hazards. Known as "intelligent drilling," use of real- time logging information provided by LWD is enabling stronger, more successful wells both onshore and off. LWD transmits logging measurements at regular intervals while drilling is taking place. Data is transmitted to the surface through pulses through the mud column (also known as mud pulse of mud telemetry) in real time.
- 15. LOG ACQUISITION AND PROCESSING Logging While Drilling Data Transmission 1) Mud Pulse Telemetry (Pressure pulses) 2) Electromagnetic Telemetry(Using conductivity of drillpipe) 3) Wired Drill Pipe(The future. Faster and better, but delicate)
- 16. LOG ACQUISITION AND PROCESSING The instrumentation necessary for bore-hole logging is housed in a cylindrical metal tube known as a Sonde. Sondes are usually suspended in the well from an armored multi-core cable. They are lowered in from the top to the base of the bore-hole as readings are taken at predetermined regular intervals. In many surveys, the Sondes are first lowered to the base of the well and readings are taken as the Sonde is winched (pulled) back through the section. Recording can either be analog or digital but analog presentation is compulsory for interpretation. The surface instrumentation including recorders, wire-line cable drums etc is usually installed in a logging truck located near the wellhead. The parameters of a formation to be determined from well logging include: Type of formation (sand or shale); Thickness of formation Porosity and permeability of formation Type of pore fluids/ratio of water to hydrocarbon saturation. Oil-water contact (boundary) within a reservoir (OWC) or Gas-oil contact (GOC). Reservoir-shale contact; strata Dip
- 17. Wireline Vs LWD • Wireline – small, light and delicate – since the 30s – high data speeds – easy communication – good borehole contact – powered through cable – takes time – after-the-fact – specific coverage – problem at high deviation – susceptible to hole condition • LWD – big, heavy and tough – since the 70s – slow telemetry – limited control – subject to drilling – batteries and mud turbine – transparent to drilling – real-time – azimuthal – can log in any direction – more capable in tough environs. LOG ACQUISITION AND PROCESSING
- 18. LOG ACQUISITION AND PROCESSING LWD and MWD Logging While Drilling – petrophysical data Measurements While Drilling – directional surveys – drilling mechanics data – real-time data transmission
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- 20. LOG ACQUISITION AND PROCESSING A significant problem with mud pulse telemetry is that its susceptible to downhole and uphole noise. Downhole noise can be drilling and bit noise, shocks, pulser jams. Uphole noise can be from the mud pumps, electronic equipment on the rig. The image on the left is partially mislabelled: the lower indicator should read “drilling noise”, not “electrical noise”.
- 21. LOG ACQUISITION AND PROCESSING At the same time, engineers can examine the smoothness of drilling, the effects of mud erosion on the pulser, and even detect washouts (where leaks develop between connections of drill pipe or collars, and threaten to sever the entire drillstring). The engineer can also observe what the driller is doing: drilling on bottom, reaming the hole, pumping at different rates, etc. Analysing these kinds of raw signals let the alert engineer determine which downhole data are accurate or spurious.
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- 23. There are some petrophysical parameters that cannot be measured directly and some that can be measured directly from well logs. Parameters that can be measured directly are: density, net/gross thickness, depth, resistivity & internal diameter. Parameters that cannot be measured directly are: porosity, permeability, water saturation & hydrocarbon saturation Data processing takes place: • During acquisition • In the logging tool itself • In the surface acquisition unit • In post-acquisition processing at computing centers LOG ACQUISITION AND PROCESSING
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- 26. Congratulations!!! You have come to the end of this section.