ISIP: Instantaneous shut-in pressure (ISIP) is estimated to be the pressure after the pumps are shut down during a hydraulic fracture, and the beginning of a pressure decline. The value of the ISIP affects the interpretation of the reservoir characteristics so the determination of an accurate ISIP is crucial.
Fracture Gradient: It’s the pressure, beyond which the resistance of the rock is overcome allowing a fracture to propagate. And importantly, it’s a pressure at a depth.
Instantaneous Shut-in Pressure, or ISIP, is a valuable set of data that until a few years ago, wasn’t even possible to curate.
Inside the Petro.ai Treating Pressure Prediction App, ISIPs help you design your next well. It’s part of the full Petro.ai package that takes you from discovery to design to dollars for every part of your reservoir.
Dr. Nitin Chaudhary, Senior Data Scientist at Petro.ai, explains, “When we’re going in and designing the next well, if we use ISIP data, we can have a very good idea what the fracture gradient looks like at that specific location where we want to drill the well. But that absolute value is not the only reason why ISIP is important. The ISIP trends also have significant diagnostic value in understanding your full reservoir potential.”
“When we fracture a rock, when we start pumping fluid beneath it, we monitor the pressure as we’re pumping the fluid. We keep monitoring that pressure and once we’ve initiated the fracture and shut off the pumps, the pressure falls. Some part of that fall off signature, which we call instantaneous shut-in pressure, ISIP, indicates where we stopped applying force to the rock. The rock is an elastic surface and as soon as we stop stretching, it tries to close in on us. That closing forces a pressure back on the fluid we have pumped. That is the event or the signature that you get in the fall off which is the pressure we initially overcame to fracture the rock.
“So now, we’ve fractured all these wells in the past. We’ve been fracturing for more than a decade and have a large amount of collected pressures. We have that data in hand. So how can we do a look back on it? How can we look at that pressure signature while we were pumping and find the ISIP point across time?
Treating Pressure Prediction App: ISIP Selection
“That’s where it becomes extremely important to have something like Petro.ai’s Treating Pressure Prediction App. If you were to do this manually and you have hundreds of wells that you’ve fracked over the last two years and you have the pump curve data for those wells, the pump curve pressures, you would have to manually go in and look at the pressures, find the fall off point and manually pick a point on there. That’s how you would have to curate that data without the Petro.ai connection.
“The ISIP App lets you use all your pressure data.
You have hundreds of wells worth of data and now with Petro.ai, you have a system where you can upload it quickly.
The app automatically picks that fall off point for you. The entire process becomes automated. Engineers don’t need to go look for files and then plot them or look for the ISIP value. Petro.ai curates all of that when you run the app. All you need to do is QC it and then we have easy ways to download the information. From there, you apply your own frac hit grading profile from the past wells that you’ve drilled.”
ISIP Trends: The Bigger Picture
Dr. Chaudhary continues, “ISIPs and fracture gradients are inferred information. Unless we drill and take a piece of core, literally take a piece of rock out of there, bring it back upstairs, and do some laboratory testing, we can’t be completely sure. But even then, there are all sorts of issues with using a coring because there’s a different environment at 10,000 feet below the surface. When you bring it to the surface it changes the variables. It’s not reliable. And it’s expensive. Companies wouldn’t have that kind of data. If they did, they would only have it at one or two locations, especially not the entire basin.
“Although correlated, there is definitely some debate about whether the ISIP point represents the fracture gradient or not. The rock that you’re drilling through and extracting the oil from changes, the rock’s properties change with the intrusion. It matters what’s on top of it and what’s been drained from it. The state of the fracture gradient differs at every location. So, what becomes equally relevant is to look at the trend in the ISIP values. Is it increasing as you go deeper or staying even across the lateral? Is it increasing or decreasing or oscillating around an average value? That trend has as much analytical worth as the absolute value itself.”
Using the trend information of ISIPs changing over time and the ISIP value, well spacing can be evaluated from this readily available completions data, which has been underutilized until recently. Dr. Chaudhary completes the picture, “Now with Petro.ai, there’s a quick and easy way to use ISIPs that makes it an integral part of any company’s fracturing process. We even go a step further than other companies with some automatic diagnostics and one of them is being able to pick the ISIP value. Internally we use the stress gradient that we build from in several different places in the platform. We use it in our Treating Pressure Prediction App. We also utilize it in our Pad Scenario Designer App. Petro.ai allows for a complete analysis from well spacing concerns to EUR to ROI.”