Logging Run
A logging run is a single descent and ascent of a wireline logging tool string into the wellbore to acquire petrophysical measurements over a specified depth interval, encompassing tool deployment, downhole calibration, the primary upward-logging pass at controlled speed, any required repeat sections for quality assurance, and tool retrieval to the surface, with each run representing a discrete operational unit charged against rig time and forming the basis of a well's log suite.
Key Takeaways
- Combining multiple measurement tools into a single tool string (combo run) reduces the number of logging runs required, cutting rig time and non-productive time (NPT), which is especially important in offshore wells where rig rates exceed $200,000 per day.
- A repeat section of 150 to 300 feet is run at the beginning of each main pass to verify tool repeatability; the repeat must overlay the main pass to within tight tolerances before the log is accepted as valid data.
- Logging speed directly affects vertical resolution: slower speeds allow more measurement samples per foot, improving thin-bed resolution, while excessive speed causes depth-smearing and missed thin pay zones.
- Open-hole logging runs must be planned before casing is set, as cement behind casing changes the measurement environment and limits the reservoir parameters recoverable by cased-hole tools.
- In horizontal wells, wireline logging runs are often replaced by logging while drilling (LWD) tools because wireline tools cannot reach the horizontal section under gravity alone without conveyance systems such as tractors or coiled tubing.
Fast Facts
Typical logging speed for resistivity/porosity combo: 1,800 to 3,600 feet per hour. Borehole imaging tools: 900 to 1,800 feet per hour. Formation tester runs: stationary at test stations. Typical repeat section: 150 to 300 feet. Average open-hole wireline logging cost per run (offshore): $25,000 to $80,000 in tool charges plus rig time. Maximum tool string length for a single run: typically 100 to 150 feet. Operating temperature limit for standard tools: 175 degrees C; HTHP tools: up to 260 degrees C.
Tip: When planning a logging program for a complex HPHT or deepwater well, schedule the formation pressure testing run as a standalone or semi-standalone operation rather than adding it to an already-heavy combo string; the time spent repositioning the tool between pressure test stations is difficult to predict and frequently causes the combo string to exceed its temperature limit while waiting on downhole.
What Is a Logging Run
A logging run begins when the wireline engineer rigging up spooling equipment at the surface and ends when the tool string is retrieved and laid out for inspection. Between these points, the logging tool descends to the target depth on a multi-conductor wireline cable, acquires measurements during the upward pass (logging tools measure on the way up to keep the cable in tension), and records data in real time to surface acquisition units.
Open-hole logging runs are performed before setting casing and provide the foundational reservoir characterization data: porosity, lithology, fluid saturation, borehole geometry, and formation pressure. Cased-hole logging runs are performed after casing and cementing, targeting cement evaluation, production monitoring, casing inspection, and through-casing saturation measurements. Each category uses different tool physics and serves different purposes in the well's lifecycle.
How Logging Runs Work
Before deployment, the logging engineer configures the tool string by selecting the individual sondes to address the well's objectives, connecting them mechanically and electrically, and running pre-run surface calibrations using standard reference materials (calibration pits, check sources, or master gauges). The assembled tool string is run downhole on the wireline cable at transit speed (faster than logging speed) until it approaches the target depth.
The main logging pass proceeds upward from total depth or the casing shoe to the surface. Logging speed is controlled by the drawworks or a surface motorized sheave to maintain the rate specified in the tool's operating manual. Depth control is maintained by a calibrated wheel encoder on the wireline cable, correlated to a magnetic casing collar locator (CCL) in cased hole or to a natural gamma ray correlation log in open hole. After completing the primary pass, the tool is lowered again to run the repeat section over the deepest portion of the interval for quality check comparison.
Log quality issues detected during the run include erratic curves from tool sticking or jerking, cycle skipping on sonic logs from poor borehole contact, high baseline noise on resistivity from metallic junk in the hole, or tool shorts from cable damage. When quality issues are identified, the run may be re-logged or the affected interval annotated for reduced reliability. Final log headers document tool serial numbers, calibration data, run parameters, and any operational anomalies.
Logging Runs Across International Jurisdictions
In Canada and the WCSB, open-hole logging programs for Montney, Duvernay, and Viking wells are designed to satisfy both the operator's petrophysical objectives and AER reporting requirements. The AER's Directive 079 (Well Data Filing Requirements) mandates submission of wireline log data in LAS format to the Well Data Management System (WDMS) after each well is completed. Alberta's horizontal well programs often use LWD for formation evaluation in the lateral, supplemented by a wireline trip in the vertical or curve section for high-resolution porosity and resistivity. Logging costs are a significant variable in WCSB well economics, particularly in remote northern Alberta and Northeast BC locations.
In the United States, logging program design follows standard industry practice with no federal mandate for specific tool suites, though the BOEM requires certain minimum log submittals for offshore wells drilled on federal leases. Onshore, state agencies such as the Texas RRC, the Colorado Oil and Gas Conservation Commission (COGCC), and the Wyoming Oil and Gas Conservation Commission have their own log filing requirements. Major service companies (SLB, Halliburton, Baker Hughes) provide standardized logging menus for Permian, Eagle Ford, and Haynesville wells optimized for the specific lithology challenges of each play.
In Norway, Sodir (Norwegian Offshore Directorate) mandates log submission under the Resource Data Collection regulation, requiring digital log files in LAS or DLIS format be submitted within specified deadlines after well completion. Norwegian well programs on the NCS follow detailed logging requirements for each well type (exploration, appraisal, development), with specific tool suites required by license conditions in some blocks. The Norwegian Oil and Gas Association's standard logging program for North Sea wells is widely used as a template by Equinor, Aker BP, Vaar Energi, and other NCS operators.
In the Middle East, Saudi Aramco's SAES engineering standards define logging programs for Arab-D, Khuff, and Jilh formations in detail, requiring specific tool combinations and quality control tolerances. Saudi Aramco's in-house wireline services subsidiary operates logging units across the kingdom's onshore and offshore fields. In Abu Dhabi, ADNOC and its subsidiary ADCO define logging programs through technical specifications in drilling contracts; carbonate reservoir characterization in the UAE frequently requires borehole imaging (FMI, OBMI) and NMR logs in addition to the standard triple-combo, making multi-run programs standard on appraisal wells.
Synonyms and Related Terminology
A logging run is sometimes called a wireline run, a log run, or a tool run. The complete set of logs acquired in a well is the log suite. Individual tool configurations are called tool strings or combo strings. Related operations include wireline logging, logging while drilling (LWD), and measurement while drilling (MWD). Data quality concepts include repeat section and depth correlation. The log data file formats LAS (Log ASCII Standard) and DLIS (Digital Log Interchange Standard) are the standard submission formats. Related services include formation pressure testing and borehole imaging.
Frequently Asked Questions
Why are logs run on the way up rather than on the way down?
Logging tools are pulled upward by the surface drawworks, which keeps the wireline cable in constant tension and ensures a steady, controllable logging speed. Running downhole, the cable would need to be pushed against gravity, causing slack, kinking, and uneven cable feed that makes depth control unreliable. Pulling upward also keeps the tool pressed against the borehole wall on the low side in deviated wells, improving pad contact for resistivity and density tools.
What happens if the logging tool gets stuck in the well?
Tool sticking (differential sticking against a permeable zone, or mechanical sticking in a tight borehole) requires the logging engineer to apply jarring force through the wireline cable or to use a downhole jar tool if equipped. If the tool cannot be freed, the cable may be cut at surface and a fishing operation mounted to retrieve the tool. In severe cases, the stuck tool must be milled over or the interval sidetracked. This is a significant risk in high-angle wells and in wells with highly overbalanced drilling fluid that promotes differential sticking.
Why Logging Runs Matter
The data acquired during logging runs forms the permanent petrophysical record of a well and underpins all reservoir characterization work: porosity models, saturation models, net pay calculations, and the calibration of seismic inversion products used to map the reservoir between wells. Poor planning of logging runs, whether from skipped tools, excessive logging speed, or inadequate quality control, can leave permanent gaps in the dataset that reduce confidence in reserves estimates and increase development drilling risk. As wells become longer, hotter, and more expensive, the discipline of logging run planning and quality assurance has become a specialized engineering function with direct impact on asset value.