Specific data processing and interpretation workflow of production/injection history and permanent downhole gauges data based on unit-rate transient responses, usually acquired from multiwell deconvolution.
It includes the following stages:
PDG data filtering |
Multiwell deconvolution |
Formation pressure history reconstruction (from deconvolution) and NFA Pe forecast (from convolution) |
Productivity index history reconstruction (from deconvolution and NFA PI forecast (from convolution) |
Interference history reconstruction (from deconvolution) and NFA pressure interference forecast (from convolution) |
UTR diffusion modelling |
The MRT workflow is following:
- Collect flowrates and bottom-hole pressure (BHP) which are normally available with permanent downhole gauges (PDG)
- Data filtering
- Filter the data for overshoots
- Filter the BHP data with wavelet thresholding to reduce the noise
- Decimate the BHP data (usually 10:1 or 100:1)
- Translate the surface rates to downhole total rate qt with account of BHP at any moment of time
- Synchronise total flowrate qt variations with BHP variations
- Primary Analysis
- Filter out shut-ins and hold drawdowns only
- Create material balance (BHP and Pe vs cum Q) and IPR (BHP vs qt) diagnostic metrics
- Assess dynamic drainage volumes Ve for all wells – the volumes which well is currently draining with account of interference with other wells
- Identify the zones of constant productivity index (PI = const), Steady-states (SS) and pseudo steady-states (PSS)
- Deconvolution
- Convolution and analysis
- Reconstruct formation pressure history
- Reconstruct productivity index history
- Validate if PI is constant and repeat deconvolution exercises over various time intervals if required
- Analyse rates correction and check if it is within the metrological limits and raise allocation concerns and/or advise the corrections
- Create unit-rate spider-plot – a pressure impact diagram showing how one well with unit-rate would be varying the pressure in another well over time
- Create historical rates spider-plot – a pressure impact diagram showing how one well was varying the pressure in another well over time
- Create historical rates pressure interference map showing a current and cumulative impact from one well on another
- Create oil IPR at different formation pressure markups and analyse production optimization potentials
- Analytical modelling
- Perform analytical pressure diffusion modelling of all DTR/CTR using log-derivative log-log plots
- Assess potential drainage volumes Ve,max for all wells – the volumes which well would be draining in case it would be the inly producing well in the field
- Assess well drainage and cross-well transmissibilities and compare them against each other and against the OH log interpretation on the map
- Analyse additional diffusion model parameters (skin-factor, fracture length, horizontal length, permeability anisotropy) against expectations
- Additional studies
- Production forecasts
- Generate formation pressure and bottom-hole pressure forecasts based on NFA production/injection rates
- Generate formation pressure and production forecasts based on constant BHP
- Additional forecasts based on various BHP and production scenarios
- Numerical pressure tests
- Create N2 numerical pressure test scenarios for each DTR and CTR
- Check simulated DTR/CTR against deconvolved DTR/CTR in log-derivative diagnostic plots to understand where exactly numerical model may have discrepancies
- Try various model boundaries, barriers and reservoir properties to improve the match
- Production forecasts