• Yuri Fairuzov

One of the Reasons of Why Horizontal Wells Underperform, Part I: A Higher-Than-Expected GOR

Updated: Apr 23

Slotted liner completions are the most common devices used to prevent and control sand production in horizontal wells. We are currently delivering solutions aimed at preventing MIC and chloride attack caused by solids and stagnant water in offshore oil pipelines, based on Ultra-High Definition simulations of 3-phase oil-water-solids flow (NACE Paper 2019-13250). When we applied this approach to analyze sand transport in a horizontal well, we found that in the portion of the lateral adjacent to the well toe the slotted liner may be completely plugged by formation fines (inside) and completely covered by sand (outside), as shown in the figure at the top of this page. The wellbore fluids flow in the upper part of the annular space formed between the liner and the bore of the well. A localized formation collapse on the liner or sand control screens may result in a complete blockage of this portion of the lateral. Simulations of 4-phase gas-oil-water-proppant flow revealed similar results in horizontal multistage hydraulically fractured wells after the flowback period.

The blockage of the lateral may result in an uneven inflow profile and the development of a low-pressure zone within the formation in or near the heel section of a horizontal oil well. If this happens, the production GOR will grow abnormally over the lifetime of the well. A number of recent reports show that unconventional fields are getting gassier as wells age and oil output declines.

Shale wells produce a spew of oil when they’re first fracked, but over time, production falls — sometimes as much as 70% in the first year — and gas becomes a bigger part of the mix.

The Permian Basin is getting gassier as wells age and oil output declines by Rachel Adams-Heard and Catherine Ngai, Bloomberg, Dec 24, 2019

Therefore, an in-depth understanding of proppant transport along the lateral is a key factor for a timely diagnosis of this problem and the development of mitigation strategies to restore well productivity and maximize expected ultimate recovery (EUR).

If you found this article helpful, you may be interested in learning how the simulation of simultaneous flow of gas-oil-water-proppant in the lateral is carried out to address the described problem.

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