Considering that success or failure of unconventional exploration is largely dependent on drilling horizontal wells in the right area and fracturing efficiently, and considering also that geomechanical modeling facilitates these processes, it is easy to see that when industry professionals have a better perspective of the subsurface mechanics, the better chance they have for increased production.
That, said Puneet Seth, a doctoral candidate studying petroleum engineering at the Hildebrand Department of Petroleum and Geosystems Engineering at the University of Texas at Austin, is the point of geomechanical modeling: safer drilling and increased production. Such modeling is even more important, the more acute the changes in porosity and permeability, such as in compacting reservoirs or in high-pressure injection operations.
“It gives geoscientists and engineers quantitative estimates of important parameters,” he said.
The field of geomechanical modeling has evolved from being used on a regional scale, to understanding the mechanical properties of the Earth’s crust, to specific field scale applications. For example, in the petroleum engineering industry, geomechanics is used to predict important parameters, such as in-situ rock stress, modulus of elasticity and a variety of other applications. In unconventional reservoirs, typically, pilot wells are drilled to obtain important geomechanical parameters and build models that facilitate the drilling and stimulation of future wells in the reservoir. In conventional reservoirs, the technology is particularly effective in solving well-bore stability issues (in softer rocks).
“With each new well drilled,” Seth said, “the operator has more data points and a better knowledge of the geomechanical properties of the reservoir which are used to update the initial geomechanical model, and that allows the updated model to paint a more accurate picture of the subsurface.”
This helps in drilling and stimulating future wells more effectively and obtaining even more data to update the model.
Changing Demand for Geomechanical Modeling
Of course, the whole notion – in fact, need – of modeling has changed recently, as there is so much more on the line and so little room for error.
“Due to the COVID pandemic,” Seth said, “a decrease in demand of oil and gasoline caused the oil prices to plummet to negative values for the first time in history. This has certainly limited the amount of crude oil produced by operators.”
And at such times there isn’t a lot of new data available for geomechanical modeling, nor are operators doing a lot of geomechanical studies.
“In fact,” said Seth, “funding for geomechanics projects is perhaps the first thing that is slashed, when oil prices are low, since the operators need to cut costs and invest in other areas, like production engineering, to produce optimally from already existing wells.”
All this means that since operators choke back the wells and even shut-in some wells, the rate data and pressure data during the cut-back are typically used only as monitoring tools.
“This involves use of conventional/traditional techniques used in the field of petroleum engineering – like rate transient analysis – and they are effective,” said Seth.
When the industry is not contracting, however, the geomechanical models are far more utilized.
“The geomechanical models form an essential component of a feedback loop that allows for better drilling and stimulation of new child wells and increasing productivity of current parent wells.”
Seth, whose research at UT is focused on analyzing pressure interference between fractured wells in unconventional reservoirs using geomechanical modeling and reservoir engineering techniques, said such modeling has allowed him to understand the mechanisms that cause offset well pressure responses during fracturing.
“Using geomechanical modeling, I was able to understand the mechanisms (and even combination of mechanisms) that result in offset well pressure responses during hydraulic fracturing, which were previously thought to be not present or were not well understood,” he said.
Before starting his doctoral studies in 2016, Puneet worked as a geoscientist in Nigeria. After completing his integrated master’s degree program in geology at the Indian Institute of Technology, he worked with Shell, ExxonMobil and BP during several summer internships. He is already scheduled to join Shell full-time as a geomechanicist after receiving his doctorate.
At this year’s Unconventional Resources and Technology Conference in Austin, Seth is scheduled to be part of a technical session entitled “Diagnostics and Monitoring with Geomechanical Models” and present on “Rapid Analysis of Offset Well Pressure Response During Fracturing: Distinguishing Between Poroelastic, Hydraulic, and Frac-Hit Responses in Field Data using Pattern Recognition.” He will address issues related to pressure interference between fractured wells in unconventional reservoirs and specifically about analyzing offset well field pressure data during hydraulic fracturing.
“Some of the common misconceptions involved,” he said, “are related to the mechanisms that create offset well pressure responses. My talk will attempt to clear these misconceptions and provide a workflow to characterize offset well pressure responses during hydraulic fracturing better.”