This chapter provides instructions on gathering and processing measurements using the Double Combo tool.
Log presentations are included at the back of the chapter.
Introduction
The Modular Neutron Porosity tool is the first MWD nuclear source measurement commercialized by Teleco. Instead of relying on existing wireline technology to develop this tool, Teleco chose to advance and push the existing formation evaluation technology higher. This tool not only incorporates state-of-the-art detectors but also utilizes Teleco's modular design for advanced formation evaluation tools. This tool utilizes a 5 Curie Americium241Beryllium neutron source, which emits a cloud of neutrons into the surrounding formation as the tool advances in the wellbore.
Returning neutrons are sampled by near and far detectors and are used to infer formation porosity. Although this tool indirectly measures porosity, it is used more frequently for identification of hydrocarbons (specifically gas). In the presence of gas, the neutron porosity response
characteristically decreases (reads lower porosity). If this measurement is combined with a density porosity measurement (which is not affected by hydrocarbons), a characteristic cross-over pattern between the two log traces develops (whereby the neutron porosity trace falls below the density porosity trace). It is this characteristic cross over pattern that log analysts look for when evaluating potential (gas) reservoirs. This sub is typically located above the propagation resistivity sub in a double combo
configuration and above both the density and propagation resistivity subs in a triple combo configuration.
Internally, the tool uses two (near and far) solid state Li6glass scintillators coupled with photomultiplier tubes to detect incoming neutrons. A state of the art 256-multichannel analyzer is used to detect neutrons in the correct energy window and to strip away unwanted detected gamma rays. A
Double Combo Log Quality and Data Management Standards programmable gain amplifier also ensures proper peak location at elevated temperatures. This tool is modular in design, which means the detector and associated electronics are housed in its own sub. Electrical power and communications from the main MWD collar to the modular tool sub occurs over a single wire bus. This single wire bus maintains communication from sub to collar via conductive contact rings mounted in the shoulder of each sub and the main MWD collar. As a result, this sub can be conveniently added or removed from the Teleco bottom-hole assembly as needed at the rigsite.
Mud Types
All mud systems.
Borehole Correction Inputs
Gamma Ray
Tool size, hole size, mud weight, %K (potassium content), gamma API correction factor.
Dual Propagation Resistivity
Tool size, hole size, resistivity of the mud Rm , and constants (base offsets and temperature characterization constants).
Modular Neutron Porosity
Tool size, hole size, mud density, borehole salinity.
Data Editing
Editing of Realtime Data
Editing of realtime MNP data is not allowed. The realtime formation records are needed to accurately assign depths to the memory data. In the event severe decoding problems exist and the quality of the MWD log is lowered, editing is allowed provided the logging engineer has consent from the customer. In this case, the logging engineer is required to notify the Teleco office, then notify the client and request consent to edit the MWD log. If editing takes place, the engineer shall maintain a separate copy of unedited raw data that he shall use for processing memory data. Any and all editing should be prudent. If data is edited, it should be removed from the database. Under no circumstances should the data be replaced or
Log Quality and Data Management Standards Double Combo altered. It is preferred that questionable data remain in the database. This data should be identified and referenced on the log as such with a remark.
Editing of Memory Data
This is strictly prohibited. There are several reasons for this. We should let the client decide whether the data in question is useful to him or not. It is our job and responsibility as logging engineers, however, to identify data that is most likely in error (for whatever reason) and documenting this as such on the log. If the client requests an edited memory log with suspect data removed, a separate log should be made and documented as such. The LIS tape should contain all of the original memory data.
When an interval of questionable data is recorded and identified, the client should be notified and a relog should be recommended. The concept of re-logging a particular interval to determine the repeatability of re-logging sensors is a standard practice in the logging industry. In order to establish repeatability, it is important to relog a zone where the log response is not in question in addition to relogging the questionable zone. Discuss this with the client. If the client declines to relog the interval, document this as well as the questionable interval on the Remarks page of the log.
Depth Shifts
Make sure logging depths are as accurate as possible. This is crucial for this service. Make depth shifts in the database where necessary. Anytime depths differ at a depth at kelly down by 1.0 foot (0.45 meters) or greater, a depth shift should be performed. Depth shifts can be minimized by
frequently calibrating the Kelly Height sensor at kelly down and updating the depth at kelly down at every connection.
Data Management
M-SERIES
A raw database file should be stored on the hard disk (Winchester) and a raw file backed up to disk. In the event that editing of the MWD data occurs, a copy of raw unedited data shall be maintained for processing memory data (see “Data Editing” above). If a Winchester is not used on the rigsite, a raw database file also should be backed up to disk. Provide all necessary information on every disk label, and use an easy to follow sequential numbering scheme for labeling disks.
Double Combo Log Quality and Data Management Standards MDMS
Two file types need to be backed up to disk. These are the raw memory dump data and the XFER file. Both of these need to be backed up on a run by run basis.
P-SERIES
The database file should be backed up to tape periodically during the job.
Both edited and raw data are maintained in the same database, so there is no distinction between the two like M-SERIES.
HPUTIL
When M-SERIES (MWD data), MDMS XFER files (RWD data), or P-SERIES files (MWD or RWD data) are converted to binary files for plotting with MPLOT, then several file types should be backed up to disk.
These are as follows:
• binary.* (includes .fil, .apd, .uni, .idx),
• *.cfg (HPUTIL Rev. 2.1 or greater)
• setup.fil (Mplot/Wplot formats...formally newplot.fil)
• log.fil (Makelog/Head/Minihead formats)
• tvddata.fil
• newplot.fil (use with HPUTIL versions earlier than Rev. 2.1)
• header.fil (use with HPUTIL versions earlier than Rev. 2.1)
• comment.fil
These files can be compressed using PKZIP and backed up to disk using FASTBACK with the program Getdata (see “Getdata Disks” on page 1-4).
Rigsite Data Processing
Smoothing and/or Averaging M-SERIES
None applied to the database. User selective smoothing or averaging can be applied when plotting (see log formats for recommended curve
smoothing).
Log Quality and Data Management Standards Double Combo MDMS
MDMS processes raw memory dump data with MWD data and creates an XFER.FIL. Use MPLOT Utilities in HPUTIL to process XFER File into binary file. Use Squeeze to remove backplots and average data on a 0.25 feet (0.1 meter) interval (see “Squeeze” on page 8-5).
P-SERIES
None applied to the realtime database. User selective averaging (averaging on/off, it is recommended to select averaging). Propagation resistivities are block averaged on a 0.25 feet (0.1 meter) interval. See “Filtering” below for exclusive filtering routines applied to neutron porosity and gamma ray data). During processing of data, backplots are removed. Additionally, user selective smoothing or averaging can be applied when plotting (however, if the data is processed with averaging selected, it is not recommended to smooth during plotting).
HPUTIL
If Squeeze is applied to the binary.fil, backplots are removed and data is averaged on a 0.25 feet (0.1 meter) interval. Additionally, user selective smoothing can be applied when plotting (see log formats for recommended curve smoothing).
Filtering
Hanning window filter is available only in P-SERIES 2.0 and above.
Applied to neutron porosity and gamma ray data. This routine filters as the data is placed on a 0.25 feet (0.1 meter) interval.
Other
Borehole Corrections
Applied automatically by surface software (see “Borehole Correction Inputs” on page 8-2).
Dielectric Corrections
This will be a rigsite option with P-SERIES 2.01 and above. Applied to phase difference and amplitude ratio resistivities when these data are affected by formation dielectric effects.
Squeeze
Required for non-P-SERIES databases (HPUTIL binary files). Apply to binary files before plotting final logs with Gulton plotters. Squeeze compresses the data file by removing all backplots and then averages the
Double Combo Log Quality and Data Management Standards data on a 0.25 feet (0.1 meter) interval. (For more information, see
“Squeeze” on page 1-5.) Quicken
Quicken is not required but is highly recommended for non-P-SERIES databases (HPUTIL binary files). Apply to binary files after Squeeze is performed. This application sets up indices for every 100 feet (50 meters) of log, which speeds up the depth search routine for the MEDIT editor.
(For more information, see “Quicken” on page 1-5.) ADDTSD
ADDTSD is required for non-P-SERIES databases (HPUTIL binary files).
Apply to binary file as needed during job. This application calculates the time since drilled and data density curves for MWD and RWD data.
Calculate from the phase difference resistivity (RPCM) unless otherwise requested. (For more information, see page 2-7.)
ADDTVD
ADDTVD is required on every horizontal well. This routine calculates and arranges directional data (true vertical depth) so it can be plotted as a curve.
This is an HPUTIL utility program. (For more information, see “True Vertical Depth” on page 2-8.)
WDS Quicklook Log Analysis Performed as required.
Note: No other rigsite data processing is required unless incorrect or base offsets and temperature
characterization data and/or incorrect borehole corrections have been entered into the database. If this occurs, enter the correct correction factors and
recalculate the database.
Postwell Data Processing
Before Final Logs Dielectric Corrections
Performed as required. Applied to phase difference and amplitude ratio resistivities when these data are affected by formation dielectric effects.
This can be performed either in P-SERIES 2.01 and above or WDS.
Log Quality and Data Management Standards Double Combo Inversion
Performed as required. Applied to phase difference and amplitude ratio resistivities when characterized by thin bed effects. Performed in WDS.
After Final Logs
Postwell WDS Log Analysis
Performed at clients request by Regional Log Analyst. Provides a more detailed analysis of logging data than Quicklook.
LIS ASCII File and Tape
Performed in either MDMS, P-SERIES, LOGWORKS, or WDS at customer's request.
Rigsite Calibration Verification
Required at the beginning and end of each run. Verification accomplished using the neutron verifier and verification menu's in MDMS or P-SERIES surface software. Verification data should be recorded on Calibration Verification page on P-SERIES header. Verification procedures and tolerances are currently under investigation. Therefore, they have been purposely omitted.
Quality Control
Quality Control Curves Data Density
Currently, data density is not calculated for neutron porosity or bulk density. Use the data density calculated from phase difference resistivity (RPIM). Data density (integrated) should be plotted on the quantitative log as tick marks in the depth track on the left-hand side.
Time Since Drilled
Since there should be relatively little or no difference in the time since drilled calculated from each sensor, use the time since drilled calculated from phase difference resistivity unless DPR is not present or the client requests otherwise. Plot time since drilled as a medium spot line on linear grids. This trace should be plotted on quantitative logs only.
Double Combo Log Quality and Data Management Standards Log Quality Control
You are responsible as a logging engineer to periodically evaluate the data quality of your logs. Generate quantitative logs and inspect the curves for areas that might suggest a compromise in quality. If areas characterized by poor quality are detected, notify the office (Teleco) and the client
immediately. Under these circumstances, the client should be given the opportunity to recover either lost or poorly recorded data.
Listed below are required log quality checks that need to be performed for any RWD service. If during these checks you identify a problem area, you are required to call the office for recommendations.
Note: Refer to DPR Services (see Chapter 7) for additional recommended DPR log quality checks. The DPR log quality checks should be run in addition to the MNP log quality checks.
1. Realtime vs. Memory Data Comparison: A quantitative log is required for adequate evaluation. At the end of each run after the memory data has been processed, a log should be made with the realtime and memory data plotted side by side (i.e., realtime NPCX data in track II, memory NPCM data in track III). The engineer should evaluate the log for depth shifts between the realtime and memory data. Depth shifts result when incorrect time offsets are applied before processing. If depth shifts are identified, call the office for recommendations.
Note: There may be a difference between the realtime and memory MNP log responses due to smoothing and averaging that is not applied to realtime data (see
“Rigsite Data Processing” on page 8-4).
2. Realtime vs. Relog Data Comparison
• A quantitative log is required for adequate evaluation. After a relog (second pass) is performed, it is important to plot the memory relog data with the "original pass" realtime data.
Plot realtime and memory gamma ray in track I and original pass realtime NPCX with memory relog NPCM in track III (plotting DPR data in track III is optional). Evaluate this data for depth shifts. If depth shifts are identified, call the office for recommendations.
• If memory relog data is merged with "on bottom" data, a composite log that contains the realtime "on bottom" data and the memory merged relog data should be plotted and
Log Quality and Data Management Standards Double Combo evaluated for depth discrepancies. Plot the realtime "on bottom" and the memory merged relog gamma ray together in track I. Plot the realtime "on bottom" and the merged relog in track III (plotting DPR data in track III is optional).
If depth discrepancies occur, call the office for recommendations.
Typical Log Response
Gamma Ray
The gamma ray sensor is primarily a lithology indicator. It measures the natural gamma ray radiation that is emitted from naturally occurring radioactive elements (uranium, thorium, and potassium) deposited within the surrounding formations. As it turns out, shale generally contains much higher quantities of these radioactive substances than sandstones and carbonates (limestone and dolomite). Therefore, the gamma ray sensor can in most cases easily distinguish between shales and non-shale formations.
• Shales are generally identified by high gamma ray readings (greater than 100 MWD-API units).
• Non-shale formations (sandstones and carbonates) are identified by relatively low gamma ray readings (lower than 60 MWD-API units).
Dual Propagation Resistivity
After borehole corrections have been applied and relatively standard borehole conditions exist, the following relationships between Rpdand Rat
should apply.
Permeable Zones
When Rmf< Rw , then Rpd < Rat
When Rmf> Rw , then Rpd> Rat
In both cases, the amount of separation will depend on the depth of invasion, the relative values of Rmf , Rw, and the filtrate and water saturations.
Impermeable Zones (Shales) When Rmf< Rw , then Rpd≤ Rat When Rmf> Rw , then Rpd≥ Rat
Double Combo Log Quality and Data Management Standards Dielectric Formations
Rpd < Rat
Thin Beds Intersecting Borehole at High Incident Angles (Above 60°)
Rpd > Rat
Eccentricity
Typically no effect unless a large contrast between Rm and Rtexists (either Rmmuch greater than Rt , or Rtmuch greater than Rm). Under these
circumstances Rpd< Rat .
Modular Neutron Porosity
After borehole corrections are applied, the following relationships should apply. This also assumes the correct logging matrix (sandstone, limestone) has been applied.
Clean Reservoir Rocks Filled with Either Water or Oil NPCM reads correct porosity.
Clean Reservoir Rocks Filled with Gas NPCM reads lower than true porosity.
Shale Zones
NPCM reads higher than true porosity.
Other Requirements for This Service
Surface measurement of Rmand Rmf corrected for bottom-hole circulating temperature required on a daily basis. This data should be supplied on the header of each daily log with BHCT (see “Main Header, Environmental Parameters” on page 3-8 for measurement procedures).
Log Quality and Data Management Standards Double Combo
Log Presentation
Note: All log formats listed below assume the data is either realtime or memory data that has been processed without a P-SERIES system (or with a P-SERIES system "without averaging" selected for processing) and plotted using MPLOT. In cases where a P-SERIES system was used and the data was processed using the "averaging" option, then it is recommended not to smooth during plotting.
This will result in oversmoothed logging traces. This will most frequently affect the Gamma Ray MWD API trace.
North and South America Log Presentations
1:600 AND 1:1200 ENGLISH DEFAULT LOG FORMATS (correlation) LIMESTONE MATRIX
SANDSTONE MATRIX
1. TVD: Optional trace used specifically for horizontal well applications. Scale increases from right to left.
2. TCDM: Optional curve for this presentation. Scale increases from left to right.
Track 1: Linear Track 2: Linear Track 3: Linear
Trace Track Param Ledge Redge Line Mode Smooth Pen Up Notes
1
Track 1: Linear Track 2: Linear Track 3: Linear
Trace Track Param Ledge Redge Line Mode Smooth Pen Up Notes
1
Double Combo Log Quality and Data Management Standards
1:240 ENGLISH DEFAULT LOG FORMATS (quantitative) LIMESTONE MATRIX
SANDSTONE MATRIX
1. TVD: Optional trace used specifically for horizontal well applications. Scale increases from right to left.
2. rpim/rptm: as a default, use the time Since Drilled and Data Density from Phase Difference. The output of the RPIM trace is predetermined. However, a number must be put into these parameters to prevent MPLOT from crashing. Presentation for data density is in the depth track.
3. TCDM: Optional curve for this presentation. Scale should increase from left to right.
Track 1: Linear Track 2: 2 Cycle Log Track 3: Linear
Trace Track Param Ledge Redge Line Mode Smooth Pen Up Notes
1
Trace Track Param Ledge Redge Line Mode Smooth Pen Up Notes
1
Log Quality and Data Management Standards Double Combo International Log Presentations
1:500 METRIC DEFAULT LOG FORMATS (correlation) LIMESTONE MATRIX
SANDSTONE MATRIX
1. ROPS: Default units are ft/hr. Other default units and scales are 100 - 0 m/hr, 60 - 0 min/ft, 60 - 0 min/m, 10 - 0 ft/min, 10 - 0 m/min. Default for averaging is also feet.
Metric equivalent is 2.0 (for 1:500) and 1.0 (for 1:200). Scale may need to be adjusted to accommodate the gamma ray trace (see “Rate of Penetration” on page 2-3 and
“Gamma Ray” on page 2-4 for recommendations).
2. TCDM: Default units are Celsius. Other default units and scales are 0 - 250°F.
3. TVD: Optional trace used specifically for horizontal well applications. Scale increases from right to left.
Note: WBCS (Weight on Bit) is omitted from these double combo presentations. If weight on bit is requested by the client, it is preferred to generate a separate DPR log with WBCS and ROPS in track 3 (Eastern Region default format for DPR). Placement of weight on bit in track 3
Track 1: Linear Track 2: 2 Cycle Log Track 3: Linear
Trace Track Param Ledge Redge Line Mode Smoot
h Pen Up Notes
Trace Track Param Ledge Redge Line Mode Smooth Pen Up Notes
1
Double Combo Log Quality and Data Management Standards with neutron porosity should be avoided unless there is consent from the client.
Note: Pen up intervals are in feet. Metric equivalent is 3 meters
Note: Pen up intervals are in feet. Metric equivalent is 3 meters