Memory Production Logging — What to Specify Before You Quote a Memory PL String
Buyers search memory production logging when a production or injection well needs a flow profile and there is no electric line on location, or no reason to bring one. A memory string runs on slickline or coiled tubing, records downhole, and is read at surface after the run. The RFQ that follows often says “memory PLT, complete set.” That line hides the decisions that drive price and fit: which sensors, how long the survey runs, which pressure and temperature envelope applies, and what surface kit the crew already owns.
This page is a procurement brief. For a general overview of gauges, flowmeters, and data techniques, read memory production logging tools and techniques. Here the job is narrower: turn a survey plan into fields a quote can answer, built around the CNPS memory production logging section, and send one clear brief through request a quote.
Memory mode or surface readout?
Memory mode and surface-readout logging measure the same things. The difference is when you see the data and what has to be on location.
| Memory mode | Surface readout | |
|---|---|---|
| Conveyance | Slickline or coiled tubing | Electric line |
| Data seen | After the tool is recovered and downloaded | Live, during the run |
| Power | Downhole battery | From surface |
| Fits when | Rigless or low-cost access, simple wells, repeat surveys, long stationary recordings | Decisions must be made while the tool is in the hole |
| Main buyer risk | Battery or memory runs out before the survey ends; depth tie-in is weak | Unit and cable availability, cost of the spread |
If the program needs a decision during the run, memory mode is the wrong purchase. If it needs a dependable profile at a lower spread cost, memory mode is usually the right one, provided the memory and battery budget is sized for the job.
What a memory string contains
A memory production logging string is a stack, not a single tool. On the CNPS product page, sensor data travels over a tool bus to the memory section at the top of the string and is stored in non-volatile flash under a downhole processor. A typical RFQ needs a line for each part:
- Memory section — the memory production logging tool. Published figures: 105 MPa and 177 °C maximum, 43 mm diameter, 32 Mb standard storage with larger memories in 32 Mb steps (64 Mb standard for multifinger imaging tools).
- Battery — a separate lithium battery holder. CNPS lists the memory battery holder and a battery holder with memory as separate pages for the MBH family; the published MBH temperature figure is 150 °C, lower than the memory section. Confirm which listing matches your BOM wording.
- Sensors, as the program requires — quartz pressure, platinum resistance temperature, a spinner such as the jeweled bearing continuous flowmeter or casing flowmeter, capacitance water holdup, radioactive fluid density, production gamma ray, and a casing collar locator for depth correlation.
- Surface kit — the memory control unit for programming, downloading, and battery checks (including depassivation), the MEMLOG software supplied with memory tools, and a depth record to merge with tool time, for example through a depth interface unit.
The string’s working envelope is set by its lowest-rated component, not its best one. If your well temperature is close to a published limit, say so in the RFQ so the review starts there.
Size the memory and battery for the survey
Memory production logging fails quietly when the budget is too small. If storage fills or the battery runs down before the survey ends, the remaining intervals are not recorded, and nobody finds out until download.
- Survey plan — number of passes, line speeds, stationary stops, and total time downhole, including waiting time.
- Channels and sample rate — CNPS publishes sample rates of 0.1, 0.2, 0.5, and 1.0 seconds, then whole-second steps. Faster sampling on more sensors uses memory faster.
- Published reference point — 8 Mb records six tool outputs plus pressure at one-second intervals for 126 hours. Use it as a starting point and let CNPS check your actual combination.
- Battery condition — lithium packs can passivate in storage. Plan a check with the memory control unit before the run.
Put these numbers in the RFQ. They decide whether 32 Mb is enough or a larger memory is the safer line.
Memory production logging RFQ checklist
- Objective — production profile, injection profile, or a specific question such as water entry or crossflow.
- Well conditions — tubing and casing sizes, restrictions, deviation, maximum pressure and temperature, and fluid type including H2S or CO2 if present.
- Conveyance — slickline or coiled tubing, connection type (the memory section uses a 13/16 in 12 UN thread), and whether wellhead slickline pressure control is in scope.
- Sensor list — one line per sensor; note if a radioactive density source is included so source handling, transport, and permits are addressed early.
- Memory and battery budget — survey time, channels, and sample rate as above.
- Surface kit — what you already own (interface, software, depth recording) and what must be quoted.
- Commercial — quantity, spares, destination, need-by date, and any documents the project requires.
CNPS reviews the request against published product data. Interpretation of the logs remains with the operator or its chosen analyst; this guide does not replace that work. For how production logging fits with other cased-hole surveys, see the open hole vs cased hole logging guide.
Send one brief
A useful memory production logging request fits on one page: objective, well conditions, conveyance, sensor list, memory and battery budget, surface kit, and commercial fields. Missing fields will be flagged in review, which is faster than bidders guessing at a “complete set.”
Ready to quote? Start from the memory production logging page, then send the brief through request a quote.
