Enabling Pressure Transient Analysis in Drawdown

Extracts from URTEC 2790, SPE 2020 Workshop on Rate/Pressure Transient Analysis and Distinguished Lecturer Presentation 2019/20

Lawrence CAMILLERI

With the increasing volatility in the price of oil, even low-cost onshore wells can be economically marginal and not achieve target rates of return under certain oil price scenarios and P10 or even P50 production profile forecasts.  If such market conditions persist, it will become increasingly important that all wells produce to their full potential and that a war be waged on skin and that drainage area be maximised. Where wells are fractured, maximising fracture conductivity and half-length will also be essential. It is the author’s belief that this macro-economic environment will drive an increase in pressure transient analysis (PTA) complemented by rate transient analysis (RTA) because, just as Lord kelvin stated in 1883, what we cannot measure, we cannot improve. 

Traditionally PTA requires build-ups, which is costly, both in terms of intervention and deferred production.  Fortunately, the population of permanent downhole gauges does not cease to increase and this presentation examines how downhole real time pressure and rate data enables PTA in drawdown. Such technology not only provides a source of low-cost transient data, but also the ability to obtain inflow characterisation (mobility, skin, fracture half-length and conductivity and boundary conditions)) within a few weeks of completing a well, thereby confirming the time value of information. 

To illustrate the concepts, PTA and RTA results from a MFHW (Multi Fractured Horizontal Well) case study are reviewed. This is based on data taken from URTEC 2790 paper and is particularly interesting as it demonstrates how high-quality production data can resolve a large number of unknowns. Also the history matching of flowing pressure with an analytical model yielded excellent results despite many discreet changes in flow-rate, which further enhanced confidence in the inflow characterization. Therefore if PTA can be performed in drawdown on a MFHW in unconventional tight formations, it should be relatively easy to achieve on conventional vertical wells. This workflow was applied to over 38 wells in the Bakken to generate a correlation of PV (Pore Volume) and PI ( Productivity Index) as a function of completion and fracture design thereby providing quantifiable feedback on how to drill and complete “winning” wells in a particular geological environment.

As always, economic constraints often stimulate technological creativity, and the author predicts that it will not be long before PTA in drawdown is industrialised and applied to SRP and free flowing wells with the addition of a downhole tools such as a venturis. Can we conclude that, even in a low oil price environment, economic production is possible if production is optimised utilising the right instrumentation and interpretation techniques ?

Biography: 

Lawrence has over 37 years of experience in production operations of which 27 years have been focused on artificial lift  and production optimisation in a variety of roles ranging from field and application engineer to Global Artificial Lift Domain Head for Schlumberger.  He has recently founded his own consultancy business (Camilleri & Associates) focussing on production optimisation.  He has published over 19 SPE conference papers and 5 patents covering all aspects of ESP operation such as inflow characterisation and advanced completions and was SPE Distinguished Lecturer for 2019/2020 on the topic of production optimisation. This body of work is particularly noteworthy as it combines theoretical explanations and field case studies using real time data.