Reading the subsurface: what well log depth sticks reveal on your map

Below the green of a paddock in central Queensland, the black shale of the Cooper Basin tells a story that anyone with the right tools can read. For a landholder wondering whether a coal seam gas venture might one day knock on the gate, the first question is what actually sits beneath the surface. Maps that draw lease boundaries alone only answer part of that question; the layers that show a well's path through rock answer something far more practical.

On Shale Navigator, depth sticks are the small vertical markers shown beside every well on the map. They look modest, yet each one compresses a surprising amount of geological decision-making into a single line. Tied to publicly available scout tickets, completion reports, and formation logs, these markers translate raw subsurface measurements into something a person can scan and use straight away.

The aim here is to walk through what those depth sticks reveal, what they leave out, and how they fit into the broader picture of shale development in Australia and the United States. Along the way, we'll look at how they help correlate wells across a basin, how they steer landing decisions, and where they need to be paired with other datasets to genuinely de-risk a position.

What a depth stick actually represents

A depth stick is, at its simplest, a labelled reference to a measured depth inside a wellbore. It can mark the top of a target formation, the point where drilling changed direction, the bottom of a cemented casing string, the kick-off point for a horizontal lateral, or the total depth reached by the rig. On a map, every well carries several of these markers stacked together, each tied to a specific event or geological horizon.

For Australian operators working the Beetaloo Sub-basin in the Northern Territory, or the Roseneath-Epsilon-Murteree (REM) shale package further east in Queensland's Adavale Basin, the marker that draws the most attention is the top of the target shale. Sticks tied to that horizon tell you whether a well actually intersected the prospective interval, missed above it into a younger formation, or punched through into basement. Without that single check, every other interpretation of the well is guesswork.

The shape of the stick itself often says more than the label. A short, stubby stick usually means a vertical section was logged only briefly at that depth. A long stick hugging the surface trace of the well indicates a horizontal lateral that landed and stayed within the target for thousands of metres. Reading length and orientation together gives an instant read on whether the well was designed as a vertical strat test or as a producing lateral.

Correlating wells across a basin

Once a depth stick is attached to a well, it becomes a reference point you can compare against the next well, and the next, until a basin-wide picture emerges. When several wells in the same area each carry a marker at the top of the same formation, those markers either line up horizontally, suggesting a flat-lying, undisturbed layer, or step up and down across the map, suggesting structure, dip, or faulting. Stepping through those sticks well by well is the heart of correlation work.

In the south-west of Queensland, sticks tied to the top of the Toolachee Formation in the Cooper Basin step noticeably between wells in different permit blocks. A landman weighing whether two parcels of mineral rights really sit on the same structural high can use that visual step to decide whether the southern block deserves a closer look or should be passed over for now.

The same logic applies at finer scale. Sticks marking the base of a prospective shale, the depth of an intermediate casing shoe, or the point where a lateral turned to horizontal can all be stacked to check whether a geosteering programme held its course. The well records library on the platform makes cross-comparison easier by keeping the source files for each depth stick a click away from the map symbol.

Habits that make correlation work

• Always check the operator or state agency that logged the stick. Nomenclature varies between South Australia, the Northern Territory, and the U.S. states covered by the platform.
• Plot multiple horizons at once. A single stick rarely tells the whole story; two or three stacked usually do.
• Note the date of the well. Older vertical wells drilled before modern horizontal development often carry stick depths that don't match newer landing points exactly.
• Watch for sticks that have been retroactively edited. Reports are sometimes amended years after drilling, and the map layer should reflect the latest version.

Landing zones, completion intervals, and sweet spots

For engineers and completion designers, the most valuable depth sticks are usually the ones tied to landing points and stage spacings. A landing stick tells you the depth and direction at which the wellbore rotated from vertical to horizontal within the target shale. A series of stage sticks, spaced evenly down the lateral, shows how the completion was run.

That information has direct commercial consequences. If a well shows stage sticks clustered tightly within a thin band of the formation and the rest of the lateral sits above or below it, the operator has either chased the best porosity with geosteering or had to settle for a sub-optimal landing due to dips or faults. Either way, the depth stick layer on the map tells you which wells likely produced well and which probably struggled.

In Australia's emerging plays, where appraisal activity is still thickening, depth sticks help separate genuine productive laterals from technical tests drilled for data rather than production. A well in the Beetaloo with a single, very long stick hugging the REM section reads very differently from a vertical appraisal with a handful of short marker sticks. Both are valuable, but they shouldn't be valued the same way in an economic model.

Stick categories worth pulling up first

• Top of the target formation
• Kick-off point from vertical to build section
• Landing depth at the start of the horizontal lateral
• Total depth of the well
• Stage spacing markers along the lateral
• Plug-back or abandoned interval indicators

Combining depth sticks with other well attributes

Depth sticks don't tell you everything. A stick neatly labelled "top of pay" doesn't reveal how rich the rock is, how much pressure it carries, or how it will produce over the first twelve months. For those answers, depth sticks need to be read alongside porosity logs, drill-stem tests, mud logs, and production records, ideally all linked to the same well identifier on the map.

The platform's comprehensive subsurface data catalogue is designed for exactly that workflow. Each well on the map carries links to the source documents that show where the depth sticks came from, what they were measured against, and what other data was collected at the same depth. Combining sticks with offset production history, for instance, lets you test whether a particular landing depth in a particular county historically outperformed another.

A practical approach is to open the well card as soon as you find an interesting stick, since the metadata reveals drilling date, operator, and licence number. Cross-check unusual values against the original scout ticket, as typos slip through in older wells, and treat depth sticks as a starting layer rather than a finishing one. For early-stage Australian plays, comparing U.S. analogues helps too, as the Marcellus and Barnett data sets often illuminate behaviours not yet recorded locally.

Putting depth sticks to work in decision-making

For someone making a real-world call, the value of depth sticks shows up most clearly in the speed of the decision. A landman weighing two competing lease offers no longer needs to request scout tickets and wait a week; the sticks are already drawn against each well on the map. An engineer reviewing a competitor's completion programme can see, without dialling into a data room, how many stages the operator ran and at what depths.

That speed matters more in Australia than almost anywhere else. The east coast gas market remains tight, and policy-makers are watching whether Beetaloo and Cooper Basin developments deliver enough supply to ease prices from Sydney through to regional South Australia. Decisions made on patchy data tend to come back to bite operators when production forecasts miss. Depth sticks reduce, though they don't eliminate, that risk by making subsurface assumptions visible at the moment a deal is being negotiated.

For landowners, attorneys, and smaller mineral rights buyers entering the market, the same layer offers a way to ask better questions. A quick glance at depth sticks on neighbouring wells tells you whether the local shale sits where explorers say it does, or whether the geology is more complicated than the company presentation suggested. Out in the bush, that clarity often means the difference between backing a deal and walking away from one.

To see the depth stick layer in action and pull the underlying data for your own analysis, start a subscription and unlock the full set of map layers, well records, and reporting tools. The seven-day free account is enough to explore sticks across several U.S. plays before deciding whether to keep digging into your own area of interest.