3. Crosslinked additives for acid spearhead
The purpose of NewWell's unique crosslinking additives for acid is to decrease the cost of multi-stage horizontal fracture treatment without sacrificing production. This technology allows more perforation clusters being shot in one stage without sacrificing cluster spacing and cluster efficiency. With more clusters per stage, it decreases total number of stages. For example an increase of cluster from 10 to 11 per stage can mean a decrease of almost 10% of number of stages. This decreases wireline cost, frac equipment standby time, number of plugs, and time to drill out plugs.
How does it work
Our additives increases the acid spearhead viscosity from 1 to several thousand centipoises. This viscosity increases the resistivity of acid flowing into the most open clusters, allowing more acid to be diverted into other clusters. Acid helps to remove near wellbore restricts from perforation holes, cementing sheath, and near wellbore tortuosity, thus allow clusters to be more readily taking fluid and proppant. Although these restrictions can also be removed by proppant laden fluid, the problem is that some clusters can be easily screened out by proppant before any erosion happens. Viscosified acid doesn't have this drawback.
Features of this product
-
More reliable diversion of acid: Traditionally acid is diverted into multiple clusters by increasing pumping rate once observing pressure drop on wellhead. However by then it may be too late considering that acid volume is small thus majority of the acid may have already passed the perfs. Besides sometimes pressure drop is not obvious. Using our product, the acid is fully crosslinked before entering perforation. Thus diversion of acid is rely no longer on adjusting pumping rate, but the viscosity of acid itself.
-
Specifically designed for diversion of acid to perforations: Our product is designed to fully crosslink in wellbore to maximize its diversion effect. Conditions in wellbore are different from in formation. Acid in wellbore is not spent yet, and temperature is much lower in wellbore than in formation due to cool down effect. Our system is designed to be able to fully crosslink at high acid strength and low temperature. The chart below is crosslinking behavior of our additives in 5% HCl. We first simulate wellbore cool down temperature (red curve), then use this cool down temperature profile to fine tube the crosslinking reaction, so that the crosslinking happens in wellbore, and crosslink time can be controlled to match the location of the stages.
-
Can work together with other methods, such as limited entry perforation. Currently the industry normally perforate 6 to 10 clusters per stage. Further increasing cluster numbers in one stage can lead to less clusters being treated even with extremely limited entry perforation. Our technology can combine with other perforation strategies to push the upper limit of how many clusters can be shot in one stage while ensure that all clusters are treated.
-
Improve treatment uniformity of the clusters: Down hole diagnostic tools, such as camera, DAS, and DTS all point out that not all clusters are treated equally. Some clusters receive way more fluid and proppant than others. This can lead to uneven fracture length, causing missed pay area, and fracture interference. As discussed above, viscosified acid spearhead prepares the clusters to be able to receive water and proppant more evenly, creating more uniform fractures.
-
Cost effective. Although the viscosifying additives will increase the cost of acid, total amount of acid used as spearhead is small. Thus the extra cost can be easily justified with the saving on the decreasing of frac plugs, equipment standby time, wireline cost, and time to drill out the plugs.
-
There is no extra equipment needed to deploy our system on location: The polymer-crosslinker-breaker system can be easily incorporated into your current frac operation. On location, stock acid is typically 15% or stronger and then diluted down to 5% with water phase before pumping donwhole. Our polymer-crosslinker-breaker is added in the water phase, making it easy to apply on location.
How to tell that crosslinked acid makes different
It is always challenging to tell if a technology really works as designed downhole. For this product, diagnosis tools such as fiber optic, tracer, downhole camera, are some of the methods that can be used to compare if viscosified acid does make a difference. However, these methods are expensive to use, and some have high failure ratio. Another way is to do step down tests before and after running the acid. There is no need to do step down test for every stage, Just a few stages to confirm the effectiveness of our technology.