Optimising Hydraulic Fracturing Through Simulation (ECLIPSE)

Optimising multi-stage hydraulic fracturing in unconventional reservoirs can be an arduous undertaking; especially considering high deviatoric stresses and heterogeneous rock properties.

Ahead of the Unconventional Reservoir Characterisation and Development Forum, I spoke with Dr Manouchehr Haghighi, Associate Professor & Senior Lecturer at the Australian School of Petroleum in Adelaide, about utilising simulation technology to optimise hydraulic fracturing.

The hydraulic fracturing process is usually designed by three-dimensional geomechanic software (GOHFER). GOHFER’s output data, incorporating reservoir conditions, drainage areas and fracture geometry, is critical for determining the potential of the fracturing treatment of gas production. "We need to predict the gas production out of the fracture, and that’s where ECLIPSE comes in. The output of GOHFER is the input of ECLIPSE," Dr Haghighi said.

Simulating subsurface gas production towards the actual surface leads to the crux of Dr Haghighi’s insight pertaining to the flowback process.

Indeed, it’s after injecting the engineered fluid and during the hydraulic fracturing, that the flowback process is critical.

"The gas flow needs to occur effectively; but produced water can upset the process. The flowback is crucial to optimising the appropriate methodology," Dr Haghighi remarked.

It is a very difficult task to clean up a well and rid it of produced water. However, and quite intriguingly, ECLIPSE can examine the different parameters responsible for low gas production and help to find a solution.

"One methodology is to use ECLIPSE and simulate fluid injection followed by water production back to the surface. Once you have clean up, then you can simulate gas production," Dr Haghighi explained.

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Part of the importance in pursuing such a method involves stages where water is sometimes left in a reservoir for a certain amount of time, ranging anywhere from a week to a few months; upon which the effect of this duration becomes unknown.

Water can be lost and integrate with various parts of the reservoir, rendering recovery of the fluid obsolete. The effects are potentially harmful to the immediate and surrounding environments. Essentially, sensitivity analysis can define best practice by way of determining multiple influencing factors, such as proppant reliability, gel filtration and capillary resistance to name a few.

Furthermore, such a simulation can allow for assessment of the optimal pressure drawdown for clean-up. Interestingly, however, simulating fluid production has also proven to be a challenge for many companies with projects involving hydraulic fracturing, often due to the calibre of experience. According to Dr Haghighi: "Many companies are challenged by a shortage of experts that specialise in ECLIPSE. Basic modelling isn’t hard; but validating models via history matching is where it can become difficult."

Tuning the model for validation can be an intricate process, and optimising the flowback for hydraulic fracturing by using ECLIPSE is not commonplace as an industry practice. Not compared to the traditional application of forecasting oil & gas production from reservoirs.

Dr Haghighi is working with a group of PhD students who are conducting intensive research into various methods of utilising ECLIPSE for unconventional reservoirs and history matching.

At the Unconventional Reservoir Characterisation and Development Forum, Dr Manouchehr Haghighi will present Optimisation of Multi-Stage Hydraulic Fracturing in Tight Gas Reservoirs.

Other speakers slated to present unique insights surrounding unconventional reservoir characterisation include:

• Steve Broome, Reservoir Engineering Adviser at Norwest Energy, will present a case study titled AS2 Post Frac Analysis - We’ve Forgotten What We Didn’t Know.
  
  
• Luke Connell, Research Group Leader at CSIRO Petroleum, will present Gas Storage and Diffusion Behaviour in Shale and Coal Reservoirs.