Open-hole logging measures the formation after the hole is drilled and before casing is set across that interval. Cased hole logging (logging behind casing) measures through casing and usually cement after the wellbore is lined. Open-hole data typically give a clearer view of virgin formation properties; cased-hole data answer integrity, saturation-behind-pipe, and production questions when pipe is already in place. The borehole state decides the toolset—the two methods are complementary, not interchangeable labels.
This hub compares open-hole and cased-hole logging for buyers and well planners, then routes cased-hole tool families (CCL, gamma ray, cement bond, memory production logging) to existing guides and product pages. Deep procurement framing lives on the Open Hole vs Cased Hole Logging: What Buyers Need Before They Spec Tools—keep this URL as the comparison and tool-map hub.
Open-hole logging: purpose and timing
Open-hole logs are commonly used to describe lithology, porosity, saturation, structure, geomechanics and fluid contacts before casing decisions are locked. Typical families include resistivity, nuclear porosity and density, neutron, sonic, nuclear magnetic resonance, imaging, and formation-pressure or sampling tools. The exact combination is a well-design choice, not a universal suite.
Timing is usually time-critical. Hole stability, differential sticking, lost circulation and rig-time cost constrain how long tools can stay in unsupported hole. Benefits include higher sensitivity to formation properties that casing later attenuates, and the ability to influence casing points, perforation strategy and completion design while the interval is still open. Constraints include hole quality, rugosity, invasion, mud type, temperature, well control and mechanical risk. A washed-out hole can degrade pad and nuclear measurements even if the tool string is rated for the depth.
Open-hole conveyance may be wireline, drill-pipe conveyed, or logging-while-drilling. LWD is still open-hole physics under drilling-environment corrections—treat it as a conveyance and timing choice. For sensor and product-scope language, see What Are LWD Products? Oilfield Logging-While-Drilling Sensors and Tools Explained. For measurement-while-drilling RFQ framing (trajectory/survey, not a substitute for formation evaluation), see MWD Tools for Buyers: What Belongs in a Measurement-While-Drilling RFQ.
Open-hole RFQ questions (short)
- What decision will the data change: casing point, completion, reserves, or geomechanics?
- What are hole size, deviation, temperature, pressure and mud system?
- Is wireline, pipe-conveyed or LWD required, and why?
- What environmental corrections and quality flags belong in the deliverable?
- Who owns interpretation: contractor, operator or a named third party?
Cased-hole logging: purpose and timing
Cased hole logging is used after casing is set—often called logging behind casing when the measurement path includes steel and cement. Common objectives include cement evaluation, casing inspection, saturation behind pipe, production logging, and well-integrity diagnostics. Acoustic cement-bond and ultrasonic tools, pulsed-neutron saturation tools, multi-finger calipers, electromagnetic casing inspection, and production-logging suites (spinner, temperature, pressure, capacitance or gas-holdup sensors) belong in this family when specified.
Benefits include access after the well is secured, repeatable surveillance during production, and the ability to investigate integrity without returning to open hole. Constraints include attenuation and distortion by steel and cement, reduced vertical resolution for some measurements, and the need to know completion geometry: casing weight and grade, cement, tubing, packers and perforations. A cased-hole saturation log cannot be interpreted as if it were an open-hole resistivity log.
Wireline depth of cased-hole RFQ detail—conveyance, cement bond, CCL/GR correlation, memory PL—belongs on Cased Hole Wireline Logging Buyer Guide: Cement Bond, CCL, Gamma Ray, and Memory PL RFQ. This hub only maps which tool family owns which question.
Cased-hole tool map: CCL, gamma ray, cement bond, memory PL
Use this map to pick the child page or product record—not to replace a procedure. Each family answers a different decision.
| Tool family | Typical question | Hub route (guide) | Catalogue entry |
|---|---|---|---|
| Casing collar locator (CCL) | Where are collars / depth reference in casing? | Casing Collar Locator (CCL) for Well Logging | Casing Collar Locator |
| Gamma ray (GR) behind casing | Lithology / correlation through pipe | (with CCL in wireline buyer guide) | Gamma Ray Tool Well Logging Tool |
| Cement bond / ultrasonic | Is zonal isolation evidence adequate? | Wireline buyer guide (bond depth) | Cement Bond Tool |
| Memory production logging | Where is flow / contribution after completion? | Memory Production Logging Buyer Guide: String Build, Memory Budget, and RFQ Fields | Memory Production Logging |
Do not deep-duplicate the buyer guides above. Name hole condition, objective, casing/completion geometry, temperature–pressure envelope, conveyance and deliverable format before asking which published record matches. CNPS publishes logging and wireline-related catalogue records; those pages list products—they do not select a logging program.
Open-hole vs cased-hole: side-by-side comparison
| Topic | Open-hole | Cased-hole |
|---|---|---|
| When it is run | After drilling the interval, before casing that interval | After casing (and usually cementing); also during production or workover |
| Primary use | Formation evaluation and well-construction decisions | Integrity, saturation behind pipe, production diagnostics, later surveillance |
| Main advantage | More direct formation response for many petrophysical measurements | Well is cased; measurements can be repeated over life of well |
| Main constraint | Hole stability, invasion, rig time and mechanical risk | Casing and cement in the measurement path; completion hardware |
| Cannot replace | Later integrity or production diagnostics that require cased-hole tools | Many open-hole petrophysical measurements that casing prevents or degrades |
Quick gate: if casing is already set across the interval, lean cased-hole. If you need virgin formation measurements before pipe, lean open-hole. Integrity, cement and production focus usually belong in the cased-hole column. An LWD program may reduce later open-hole wireline needs but still leaves room for later cased-hole surveillance.
Cement, casing and integrity connect the two worlds
The moment casing is cemented, the evaluation problem changes. Cement evaluation is a cased-hole task that checks zonal isolation assumptions used in well design. Poor mud removal, channels, microannulus or lightweight slurry can all change acoustic response. If cement evaluation is required, specify the tool family, logging fluid, pressure on the casing, and the acceptance criteria from the well-design basis—not a generic blog list. Casing inspection and well-integrity logs answer different questions from open-hole porosity; mixing the two in one RFQ sentence usually means the decision owner has not been named.
Production logging and later surveillance
Once the well produces, the question often shifts from “what is the rock” to “where is the flow.” Production logging in cased or completed hole uses a different tool mix: spinners, temperature, pressure, holdup sensors and sometimes noise or fibre-based methods. These surveys diagnose contribution, crossflow, leak paths or injection distribution. They do not replace the original open-hole petrophysical program. If both are needed over field life, budget and access for repeat surveys should be in the well plan. For memory-based production logging string and RFQ depth, use the memory PL buyer guide linked in the tool map—not a second essay here.
Build a logging program from decisions, not from a catalogue page
Start with the decision: casing point, completion design, reserves booking, production allocation, or integrity. Map each decision to a measurement that can actually change it. Then select conveyance, hole condition and quality-control rules. Only then compare available tools or services. A “full suite” copied from another well wastes rig time if lithology, mud system or well objective differ.
Light RFQ checklist (hub)
- Hole condition: open hole, cased hole, or both, with sizes and casing details.
- Objective: formation evaluation, cement evaluation, saturation, production logging, or integrity.
- Environment: temperature, pressure, deviation, fluid, H₂S/CO₂ if known.
- Conveyance: wireline, LWD, tractor, or pipe-conveyed.
- Deliverable: curves, images, samples, pressures, interpretation and due date.
- Standards and procedures: operator spec, calibration, depth control and witnessing.
Deliverables should include raw curves, environmental corrections, quality flags, depth control method and the interpretation model. Highly deviated wells may need tractor or pipe-conveyed logging—include conveyance as a mechanical plan. Serious procurement detail belongs on the open-hole vs cased-hole buyer guide linked in the lead.
This page does not publish tool accuracy, depth of investigation, temperature–pressure guarantees, or service-company performance figures. Those values are tool-, borehole- and vendor-specific. Use the tool specification, environmental corrections and a named interpretation procedure for decisions.
Frequently asked questions
Can cased-hole logs replace open-hole logs?
Not for every petrophysical measurement. Casing and cement change the physics. Cased-hole tools answer later questions such as integrity, saturation behind pipe and production diagnostics.
What is logging behind casing?
Logging behind casing is cased hole logging: measurements acquired after casing (and usually cement) are in the path between the sensor and the formation. Objectives and corrections differ from open-hole formation evaluation.
Is logging while drilling the same as open-hole wireline?
Both are open-hole measurements, but timing, standoff, trajectory and correction models differ. Specify which dataset is the record copy. See the LWD products page for sensor-scope language.
When is cement-bond logging required?
When the well-design basis requires evidence of zonal isolation after cementing. The tool family, logging conditions and acceptance criteria should come from that basis.
What cased-hole tools does a hub RFQ usually name?
Name the decision first, then the family: CCL for collar/depth reference, gamma ray for correlation behind pipe, cement-bond/ultrasonic for isolation evidence, and production-logging (including memory PL) for flow diagnostics. Route deep RFQ fields to the wireline and memory PL buyer guides.
How do open-hole and cased-hole programs work together?
Many wells use open-hole evaluation for construction decisions, then cased-hole cement, integrity or production surveys later. Plan access and budget for both if field life requires surveillance—do not treat one suite as a substitute for the other.
What should I send CNPS for a logging-related enquiry?
Hole condition, measurement objective, temperature–pressure envelope, conveyance, casing/completion details if cased, and the product or service group to review. Use Talk to an Engineer or Request a quotation with a named duty so the first response can address the actual envelope.
Related resources
Use the buyer guide (linked in the lead), the cased-hole wireline and memory PL buyer guides (tool map), the CCL post, and the LWD/MWD pages above as the working cluster. This hub stays comparison-first and routes cased-hole tool families without restating their RFQ depth.
Send open-hole or cased-hole status, temperature–pressure envelope, conveyance and casing details so the review can match a published record or say that none fits.
Related reading: Mud logging: tools, techniques & how it works
Frequently Asked Questions
What is cased-hole logging?
Cased-hole logging is logging run after casing is set, to evaluate cement-bond quality, perforations, production and reservoir behaviour through the casing.
What is open-hole logging?
Open-hole logging is run in a bare (uncased) wellbore to measure formation properties such as porosity, resistivity and lithology directly before casing.
What is the main difference between open-hole and cased-hole logging?
Timing and target: open-hole logging evaluates the formation before casing is set; cased-hole logging evaluates the well and production through the casing after completion.
When is cased-hole logging used?
During completion and throughout production — for cement evaluation, perforation, production logging and reservoir monitoring.
