Well Test 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

• Production log interpretation

• Commingled reservoir management using WTKI in-house software

• 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 comingled wells. Nick is author of SPE paper "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 Well Model CWM

Our Commingled Well Model (CWM) is the result of many years of experience in well analysis. This package will be a powerful tool for anyone attempting to understand commingled well flow behaviour. The Software works as a predictive or as an analytical tool:

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.             

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, see ‘Products’. For product support contact CWM@wtki.com.au.

Field Development

Resource Characterisation

  • Connected volume
    Reservoir drive mechanism
    Pressure maintenance requirements
    Well count
    Well design
    Well location
    Infill drilling
    Lift requirements
    Vertical distribution of resources (multi-layer systems)
    Surveillance planning
    Production forecasting
    Water disposal targets
    Flow assurance
    Facility design
    Offtake optimisation (e.g. coning)

Current and recent activity

• PLT interpretation Bangladesh

• Commingled well modelling & PTA onshore gas field – Australia

• PTA & Dynamic modelling of offshore oilfield – Thailand

• PTA for onshore fractured basement oilfield – Thailand

• PTA training for major operator - Thailand

• Dynamic modelling & forecasting of onshore carbonate gas field – Thailand

• Analysis of > 80 PBUs for the full field review offshore oilfields – Malaysia

A selection of sub-surface questions we have been asked – and successfully answered – over the years:

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?