WELL & RESERVOIR ANALYSIS
MAKING SENSE OF WELL TEST DATA
We use a range of tools to investigate and understand the sub-surface. We are well testers first and foremost, so one of our primary tools is pressure transient analysis (PTA); but we have also pioneered the analysis of commingled wells using our commingled well modelling (CWM) software, and we have deep expertise in the interpretation of production logs (PL). We also use nodal analysis and dynamic modelling where appropriate.
We understand well testing: we know how the data are acquired and what affects the interpretability of that data; we’ve run separators and programmed gauges and we know how flowrate calculations are made and how to QC them. We have a huge track record of making sense of well test data – whether it was acquired last week or 50 years ago – and of teasing out the answers to our customers’ tough questions
SUBSURFACE EXPERTISE
• Interpretation of well test information from exploration, appraisal and production wells (including but not limited to Pressure Transient Analysis)
• Production log interpretation
• Commingled reservoir management using WTKI in-house software (the CWM)
• Modelling of fluid influx and lift forces during and following perforation events, using the Transient Lift Model (TLM) co-developed by WTKI
• Wellbore pressure drop modelling using the Well Pressure Travserse (WPT) software developed by WTKI.
• Optimising water injection performance
• Well test, reservoir surveillance and well intervention design at the single-well or full-field level
• Independent image log processing and integration with production log and other dynamic data
All work is carried out under the supervision of Nick Last, globally renowned for his work with complex and particularly commingled wells. Nick is author or co-author of several SPE papers including "Estimating Zonal Gas-in-Place in a Commingled Well Using Results from Production Logs" which can be found at https://www.onepetro.org/conference-paper/SPE-158733-MS
COMMINGLED WELLS
When you look closely enough, an awful lot of the world’s hydrocarbon resource is produced from layered or commingled reservoirs. In a recent example of a problem solved by WTKI, a reservoir previously assumed to be a homogeneous single-layer sand turned out to have complex pressure behaviour caused by vertical facies variations. It was, in fact, a layered reservoir.
WTKI’s engineers have extensive experience of analysing, modelling and managing commingled wells and reservoirs, dating back 30 years. Roughly 75% of the projects we have been engaged on involve some aspect of reservoir commingling, and our current research focus is on new developments in multi-layer (usually commingled) transient layer testing.
In another recent example, our Transient Lift Model (TLM) – which models the evolution of forces on a perforating gun body following a perforating event – was adapted in order to understand the fluid flow behaviour with time in complex commingled wells where the influx from the new perforations crossflows into the existing open zones above and/or below. The TLM is currently used internally by WTKI for our consulting projects, but will later become available for external licensing/ On the other hand, our Commingled Well Model (CWM) is already available …
COMMINGLED WELL MODEL (CWM)
The CWM is the result of many years of experience in well analysis. This package is a powerful tool for anyone attempting to understand commingled well flow behaviour. The software works in predictive or in analytical mode:
Predictive
In predictive mode the CWM can be used to model the behaviour of a new commingled completion or to look at the effect of changing an existing completion (adding perforations or shutting a zone off, for example). The model predicts the performance of each layer including overall production and crossflows between layers. In this way it acts as a powerful completion management tool.
Analytical
In analytical mode the model can be used to match well surveillance results such as production logs or distributed temperature (DTS) data. Combining this information with the well’s production history and its initial conditions allows the user to infer how reserves are distributed between layers. This facilitates optimization of production and future field development.
The software is easy to use and is available only from WTKI. It is significantly cheaper and easier to use than other softwares and can be installed easily on any PC.
To purchase a license, contact CWM@wtki.com.au.
CURRENT AND RECENT projects
• PL interpretation of multiple commingled gas wells - Bangladesh
• PTA – Offshore Australia (deepwater, high rate gas wells)
• Perforation & lift modelling – South East Asia
• Perforation & lift modelling – Offshore Australia
• PL interpretation and Layered Reservoir Testing - Vietnam
• PL interpretation of water injection/disposal wells - Thailand
• DST troubleshooting and interpretation - Indonesia
• Commingled Reservoir Management training - Vietnam
• PTA – Offshore Vietnam (multiple DSTs on a rich gas reservoir)
• Planning and interpretation of water injection DST – Offshore Australia
• Well Modelling of supercritical injection for a CO2 sequestration project – Offshore Australia
• Lecturing on Commingled Well Behaviour – Thailand (Chulalongkorn University)
• PL interpretation of tight gas wells – Onshore Australia
• PTA for onshore fractured basement oilfield – Thailand
• PTA training for major operator - Thailand
• Dynamic modelling & forecasting of onshore carbonate gas field – Thailand
A selection of sub-surface questions we have been asked – and successfully answered – over the years:
We want to perforate undepleted reservoirs in our high-rate gas wells without shutting off the existing partially-depleted zones, but we’re worried about getting blown up the hole and trashing our wells. Can you develop a methodology to calculate how the inflow and the lift forces evolve with time so that we can avoid gun blow-up and optimize our perforation programs?
Our past attempts to perform multi-layer transient testing on our offshore oilfield have resulted in crap data and unreliable interpretations. Please help us to optimize both the data quality and the interpretation methodology so that we can actually make sense of what’s going on in these wells.
Our upcoming offshore gas development will require literally hundreds of commingled slim-hole wells that we will need to perforate, produce and evaluate. Can you guide our completion, surveillance and reservoir management strategies so we can optimize the recovery from this complicated resource?
Interpretation of our production well tests has shown a degree of faulting that’s inconsistent with the geological model. Can you help us to resolve this discrepancy?
We’re planning to develop a gas condensate field but our only well tests date from the 1960’s and the measured liquid yields show an enormous range. Can you narrow down the range of uncertainty so we can properly understand the economics of our planned development
We need a set of guidelines on how to plan, perform and analyse exploration and appraisal DST’s. Can you write them for us?
Our multi-layer, multi-well, multi-TCF commingled gas field is performing below expectations based on the resource estimates. Can you do a commingled well analysis to understand the real resource distribution and identify where we’re falling short?
Our mature oilfield is producing at 90% water cut and we need to dispose of more than 100,000 bbls of water per day. But our disposal well performance declines rapidly and the OPEX to run the disposal program is astronomical. Can you help us to optimize the entire system, stabilize well performance and reduce the OPEX?
We have a legacy set of DSTs and we need to use them to understand connected volume so we can draw up a sensible FDP. But our material balance analysis of the DST data doesn’t make any sense. Can you reinterpret all our well test data and give us a clear understanding?
The performance of our offshore oilfield doesn’t seem consistent with the geological understanding from seismic interpretation. Can you integrate PTA and PL data to identify sub-seismic features that can explain what’s going on? And then can you demonstrate this with a set of dynamic models?
We need a data acquisition program for our upcoming appraisal well that will resolve all the key uncertainties before we proceed to field development. Please design the well test program for us.
Our oil production is mostly from fractured igneous bodies and we don’t fully understand the production mechanism and have never done any PTA on our BHP data. Can you help us to understand our production system, and optimize future production, by analysing the well test and production data?
We have an onshore multi-layered gas field and the different layers have wide contrasts in reservoir properties. Can you help us to optimize the completion design? And, while you’re at it, we have some well tests that need interpreting…
Our exploitation strategy relies on long horizontal wellbores completed with wire-wrapped screens and ESP’s. But we don’t know how the wellbores are performing and the data from the ESPs is of very poor quality. Can you figure out how to get better quality downhole data and then interpret our pressure build up surveys so we can understand how our wells are really performing?
My gas well’s production rate is gradually dropping and it’s starting to cut water. Can you advise on, and interpret, a PL program to identify how to reverse the production decline and reduce the impact of water influx?
