Pick Up
Pick up in wireline logging operations refers to the specific depth at which the logging tool string is lifted off the bottom of the borehole at the start of a logging run, establishing the deepest point of the log and the initial tension state from which depth and tension measurements are referenced throughout the uphole run — a critical operational parameter because the cable tension at pick-up depth defines the baseline weight-in-hole (WIH) reading from which any subsequent changes (caused by tool drag, hole deviation, key seating, or differential sticking) are detected by the tension monitoring system during the upward logging pass; in the context of drillstring operations, pick up refers to the weight indicator reading observed when the traveling block lifts the drillstring off the slips (or off bottom) from a stationary position, with the pick-up weight typically exceeding the rotating off-bottom weight (rotary weight) and slack-off weight (lowering weight) due to static friction (stiction) at the drillstring-borehole wall contact, and the difference between pick-up weight and slack-off weight defines the overpull/slack-off envelope that the driller monitors as an indicator of stuck pipe severity and borehole friction.
Key Takeaways
- Wireline logging pick-up depth is the official bottom depth of the logging run and must be documented in the log header along with the cable tension (weight-in-hole) recorded at that depth — the pick-up depth should be set 30 to 50 feet below the deepest formation of interest to ensure that every target zone is logged on the uphole pass while the tool is in steady-state tension conditions (not decelerating from the tool-setting process), and the WIH at pick-up should equal approximately 80 to 90 percent of the tool string air weight (the remainder being buoyed by mud hydrostatic pressure and any tool drag against the borehole wall); if the WIH at pick-up is significantly less than expected (less than 60 percent of air weight), the tool string may be resting on a ledge, a bridge, or a tight spot rather than on total depth, which means the pick-up depth is shallower than intended and the deepest zone may be missed on the logging run; the service company logger must verify WIH at pick-up against the expected value from the tool string air weight and mud weight before declaring the tool has reached total depth and beginning the uphole log.
- Drillstring pick-up weight versus slack-off weight comparison is the primary diagnostic for determining hole friction and assessing stuck pipe risk during drilling and tripping operations — pick-up weight is the WOH (weight on hook) observed as the driller applies upward force to lift the drillstring from its static position, while slack-off weight is the WOH observed as the driller lowers the string and it comes to rest; on an ideal frictionless vertical wellbore, pick-up weight equals slack-off weight equals the buoyant weight of the drillstring in mud; in a deviated wellbore, the difference between pick-up weight (higher) and slack-off weight (lower) quantifies the combined friction drag force from all contact points between the drillstring and borehole wall — a pick-up-to-slack-off delta of 20,000 to 50,000 pounds in a typical Montney or Eagle Ford horizontal section is normal and consistent with the calculated drag from wellbore survey and friction factor, while a sudden increase in this delta during a trip indicates a newly developed tight spot, dogleg, or pack-off that requires investigation before continuing the trip to avoid mechanical stuck pipe.
- Free point indicator (FPI) tool operations at pick-up depth are used to determine the depth at which a mechanically stuck drillstring transitions from free movement above to stuck below — the FPI tool is conveyed to the stuck point depth on wireline and measures the differential stretch and torsion between two magnetic rings on the drillstring when surface pull and torque are applied from the rig floor; the free point is defined as the deepest depth at which the drillstring shows measurable stretch response to the applied surface pick-up force, because free pipe stretches when pulled while stuck pipe does not; from the free point depth, the back-off operation (unscrewing the drillstring at the tool joint above the stuck point using left-hand rotation and explosive back-off charges) is planned to recover the maximum length of drillstring from above the stuck point while leaving the minimum amount of fish in the hole; the accuracy of the free point depth determination directly determines the efficiency of the fishing operation — errors of 5 to 10 feet in the free point depth result in attempting to back off at the wrong tool joint.
- Pick-up overpull limits are established in the well program as maximum allowable hook loads during tripping operations to prevent drillstring parting above a stuck point — overpull is defined as the pick-up weight minus the calculated free rotating weight of the drillstring at a given depth, and the overpull limit is set at 80 to 100 percent of the tensile yield strength of the weakest drillpipe body or connection in the string at the depth of interest, accounting for the additional stress concentration from combined tension and torsion; in deep wells with high-grade drillpipe (S-135), overpull limits may be 200,000 to 400,000 pounds above the string weight, while in shallow wells with older E-75 or G-105 pipe, overpull limits may be as low as 50,000 to 80,000 pounds; exceeding the overpull limit risks parting the drillstring and converting a recoverable stuck pipe situation into a fishing job that may ultimately require a sidetrack, dramatically increasing well cost and drilling time.
- Cable tension monitoring at pick-up and throughout the wireline logging run is the primary method for detecting hole problems (tight spots, ledges, washouts) and tool anomalies (mechanical jars, stuck points) during log acquisition — the tension should increase smoothly from pick-up as the tool rises through the borehole, with transient decreases at formation boundaries where the borehole diameter decreases (caliper log confirms these) and transient increases where the borehole diameter is large (tool weight in suspension with no wall contact); a sudden cable tension drop during logging followed by rapid tension recovery indicates the tool has passed through a tight spot or ledge, and if the tension drop is severe (more than 50 percent of expected tension), the tool may have momentarily stuck and released — a pattern that warrants slowing logging speed and repeating the interval after completion; if cable tension goes to zero during an uphole pull, the tool has stuck completely and the logging operation must immediately transition to a stuck tool recovery procedure (slack off, pick up with increased force, jarring up with a mechanical jar if present in the string).
Fast Facts
The difference between pick-up weight and slack-off weight in a horizontal wellbore is approximately equal to twice the friction drag force on the drillstring from the wellbore wall contact — because friction opposes motion, it adds to the hook load when pulling up (increasing pick-up weight above the frictionless value) and subtracts from the hook load when lowering (decreasing slack-off weight below the frictionless value). In extended-reach drilling (ERD) wells with horizontal sections exceeding 3,000 meters, torque-and-drag analysis is performed before the well is drilled to predict acceptable pick-up and slack-off weight envelopes using a software model (Landmark WELLPLAN, NOV WellData, or equivalent) that integrates the wellbore survey, drillstring design, mud properties, and borehole size to calculate friction drag at every depth; if the predicted pick-up weight at total depth exceeds the hookload capacity of the rig (typically 500,000 to 1,000,000 pounds for major land rigs), the well design must be modified — either by reducing drillstring weight (using aluminum drillpipe or lighter BHA components), changing the well trajectory to reduce dogleg severity, or reducing friction with improved mud lubricity additives. World record ERD wells (Sakhalin Island, Maersk Oil Qatar wells) have routinely pushed pick-up weights to within 5 to 10 percent of rig hookload capacity.
What Is Pick Up?
Pick up has two related but distinct meanings in oil and gas operations, both referring to the act of lifting — either lifting a tool off the bottom of a wellbore at the start of a logging run, or lifting a drillstring off the slips or off the borehole bottom during drilling or tripping operations. In both contexts, the mechanical force required to initiate and sustain the upward movement (the pick-up weight or pick-up tension) is a diagnostic measurement that reveals the condition of the wellbore and the friction environment that the tool or drillstring is operating in.
For wireline logging, pick-up depth is the operational baseline — the deepest point reached, the starting tension state, and the reference from which everything else on the log is measured. For drillstring operations, pick-up weight is a daily diagnostic tool — compared against the previous pick-up, compared against slack-off weight, and compared against the calculated frictionless string weight to quantify how much friction has developed and where the wellbore problems are occurring. Both applications use the same fundamental principle: the force required to lift something in a wellbore tells you what that wellbore is doing to it.
Pick Up Weight Analysis in Directional and Extended-Reach Drilling
Torque-and-drag analysis is the engineering discipline that predicts, monitors, and interprets pick-up and slack-off weights throughout a directional well. The basic model treats each section of drillstring as a beam under combined tension, compression, bending, and torsion, with a friction force at each contact point between the drillstring and borehole wall equal to the normal contact force multiplied by the friction factor (typically 0.15 to 0.25 for oil-base mud and 0.20 to 0.35 for water-base mud). The friction factor is calibrated by comparing predicted pick-up and slack-off weights against measured values in the early vertical section of the well where the model is most straightforward. Once calibrated, the model predicts the expected pick-up weights at every depth and deviation angle, and deviations from the predicted envelope indicate either changes in the mud lubricity (mud condition issue), unexpected formation contact (ledge, dogleg, or tight spot), or string configuration changes (pipe compression or helical buckling in horizontal sections). Real-time torque-and-drag software on the rig floor displays the current pick-up weight against the predicted value continuously, enabling the driller to immediately see when the wellbore friction deviates from plan.
Pick Up Operations Across International Drilling Jurisdictions
Canada (AER / WCSB): AER's well reporting requirements include drilling daily reports that document pick-up and slack-off weights at each depth on every trip, providing a continuous record of wellbore friction conditions throughout the well that can be reviewed by AER inspection staff as part of well control or wellbore integrity investigations; in WCSB horizontal well programs (Montney, Duvernay, Cardium, Viking plays), pick-up weight trending is the primary early indicator of torque-and-drag problems that could limit horizontal reach, and major operators (Tourmaline, ARC Resources, Paramount Resources) monitor real-time pick-up and slack-off weight deviations from torque-and-drag model predictions and trigger intervention procedures (lubricity treatment, wiper trips, rotary steerable trajectory corrections to reduce doglegs) when deviations exceed 15 to 20 percent of predicted values; AER's compliance reporting for extended-reach wells includes post-well torque-and-drag analysis comparing predicted and actual pick-up/slack-off weights as a component of the wellbore integrity assessment required for wells exceeding a 60-degree departure angle.
United States (API / BSEE): API RP 7G (Recommended Practice for Drill Stem Design and Operating Limits) defines the overpull limits for drillstring pick-up operations based on drillpipe grade, size, and connection type, providing the basis for rig-specific pick-up weight limits that drillers must observe during tripping; BSEE's offshore drilling regulations require that all deepwater well programs include a torque-and-drag analysis for wells with deviations exceeding 30 degrees and that the analysis be updated when actual pick-up weights deviate significantly from predicted values, triggering a re-evaluation of the remaining planned well trajectory; Gulf of Mexico ERD wells (Perdido fold belt, Lower Tertiary deepwater plays) where horizontal displacements of 5 to 10 miles from the platform are planned require highly accurate torque-and-drag models with friction factors validated from offset well data, because errors in the friction factor propagate into incorrect predictions of the maximum reach achievable before the pick-up weight exceeds rig hookload capacity.