Simplified Formation Evaluation Log while Drilling
Describe in a simple manner how a formation evaluation log is acquired while drilling
It is a part of the rubber banding log depth use case. See example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22
Describe how a formation evaluation log is acquired while drilling
It is a part of the rubber banding log depth use case. See example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22
Convey TVD uncertainty with reference to measured depth
Bit depth is calculated by the integration of the vertical motion of the bit and drillstring. The vertical motion of the bit is a function of top drive vertical motion, block height vertical motion, change in surface hookload, and change in downhole WOB. The measured vertical motion of the top drive is affected by rig heave; the measured vertical motion of the block is affected by calibration and measurement accuracy and the top drive may be slightly bent, leading to uncertainty in block height. The integration is reset (“truthed”) on “pipe-down” using the pipe tally, which leads to jumps in measured bit depth. The integration is started with recognition of “bit on-bottom” which is remotely evaluated on surface, and is uncertain.
When surveying with an inclinometer, the inclination angle is relative to the vertical defined by the gravitational field. But when surveying with a gyro, the inclination is relative to the initial vertical before running the gyro. (A. Brooks, SPE-116155-PA)
Geo-modeler inform Drilling about TVT uncertainty from ground level #2
Convey TVD depth uncertainty.
The earth model has uncertainty on the true stratigraphic thickness of each formation layers. The TVT needs to be conveyed to the drilling team based on the planned well path.
Convey TVD uncertainty during wellbore intersection.
Driller or Operator unintentionally sidetracks a well significantly above TD, and wishes to re-enter the mother bore with the sidetracked well with minimum dog-leg severity. This operation will save having to drill an entire sidetrack to TD. There are several issues here all related to uncertainty (a) detecting that an unintentional sidetrack has occurred, (b) steering back to the mother bore at very slight small inclination and azimuth differences to avoid significant dogleg. Reference: Rio Oil & Gas Expo and Conference 2020, From TLWP: Lessons Learned From Voluntary and Involuntary Sidetracks, Rohlfs de Macedo et al., IBP0804_20 (to be published December 2020).
Drilling inform G&G Personnel about TVD uncertainty from ground level
Convey TVD uncertainty in reference to ground level
Tabulations of well survey data is typically to 2 decimal places when the uncertainty, at deeper depths, is in whole meters / feet and multiples thereof. This is misleading to the end user and subsurface modelling (especially cross correlation of pressures) suffers badly. A common representation of uncertainty on shared TVD data is needed to ensure end users take into account the real uncertainty
Convey requirements for wellbore position uncertainty associated with formation tops.
Ensure that the surveying program is sufficient to provide reliable formation tops position such that the G&G team can update reliably their earth model.
Geo-modeler inform Drilling about TVT uncertainty from ground level #2
Convey TVD depth uncertainty.
The earth model has uncertainty on the true stratigraphic thickness of each formation layers. The TVT needs to be conveyed to the drilling team based on the planned well path.
Geo-modeler inform Drilling about TVT uncertainty from ground level #3
Convey TVD depth uncertainty.
The earth model has uncertainty on the true stratigraphic thickness of each formation layers. The TVT needs to be conveyed to the drilling team based on the planned well path.
Describe in a simple manner how a formation evaluation log is acquired during a wireline operation
It is a part of the rubber banding log depth use case. See example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22
Geo-modeler inform Drilling about TVT uncertainty from ground level #1
Convey TVD depth uncertainty.
The earth model has uncertainty on the true stratigraphic thickness of each formation layers. The TVT needs to be conveyed to the drilling team based on the planned well path.
Describe how a formation evaluation log is acquired during a wireline operation
It is a part of the rubber banding log depth use case. See example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22
A set of MWD logs is to be compared to wireline logs. The MWD and Wireline log sets were measured with a different depth measurement systems, each subjected to independent stretch errors. One of the measured depths has to be stretched or shrunk by matching similar features across the MWD and wireline logs.Example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22
Through QAQC wellbore surveying procedures, new survey may be required to decrease uncertainty and/or trajectory uncertainty may be improved by using sensor fusion methods.
Geo-modeler inform Drilling about TVT uncertainty from ground level #3
Convey TVD depth uncertainty.
The earth model has uncertainty on the true stratigraphic thickness of each formation layers. The TVT needs to be conveyed to the drilling team based on the planned well path.
A set of MWD logs is to be compared to wireline logs. The MWD and Wireline log sets were measured with a different depth measurement systems, each subjected to independent stretch errors. One of the measured depths has to be stretched or shrunk by matching similar features across the MWD and wireline logs.Example from Dashevskiy et al., 2008, Dynamic Depth Correction to Reduce Depth Uncertainty and to Improve MWD/LWD Log Quality, SPE Drilling and Completions, page 13-22