Abstract for 2017 Sucker Rod Pumping Workshop

Abstract for 2017 Sucker Rod Pumping Workshop

Smart ESD with Frac Hit Early Warning

The term “Frac Hit” is an industry term defined as an interwell communication event where an offset well, often termed a parent well in this setting, is affected by the pumping of a hydraulic fracturing treatment in a new well, called the child well.

The April 1, 2017 article in the SPE Journal of Petroleum Technology (Volume 69 Issue 4) titled “Oil and Gas Producers Find Frac Hits in Shale Wells a Major Challenge” addresses current industry thinking regarding frac hits. This article can be found at this website:

This article relates that industry is more focused on protection and prevention methods, and did not discuss detection methods. The practice mentioned by Marathon termed “Decompletion”, where all artificial lift and well completion components are removed from a well, and replaced with a packer to isolate from any pressure, is a very expensive insurance policy. The big question is, which wells will require this $200,000 procedure, and which are located “safely” away from possible offset fracture treatments. Other methods such as pumping water have shown mixed results.

How do operators detect frac hits? Some operators look at the density of produced well fluids, which will change as water with frac sand enters the wellbore.The problem with surface detection is that this process is usually too late. By the time the fluid gets to the surface, and the density is determined, the frac hit has already happened. Another detection method is installing pressure gauges on nearby wells, looking for pressure increases. While this would work for wells that are shut-in, an operator would be taking a large risk doing this to an older generation vertical well, where casing tubulars were only rated to 2000 or 3000 psi. These pressure ratings were very common until the advent of high rate massive hydraulic fracturing. Many older vertical wells simply cannot have the casing closed, and then monitor the pressure, as a casing failure would be the result of the frac hit. Some install video cameras on these older vertical wells after shutting them in, hoping that a surface blowout does not occur.

What is needed is a method to detect an increased flowrate into the wellbore that is real-time, not delayed by travel time to surface, or masked by a large flowline that easily absorbs this flow increase with negligible pressure increase. Such a method has been developed, and is proposed for older beam lift, ESP, or PCP pumped vertical wells. This method identifies frac hits when they begin to cause increased fluid entry into the wellbore. This is different than waiting for these fluids to be delivered to the surface via the pumping system, and then evaluating them for density, etc. This system is not applicable to horizontal wellbores, as flow regimes due to waves and slugs will interfere with the detection method. However, for very active areas such as West Texas, where infill horizontal wells are being drilled in areas where old vertical wellbores exist, this system should be very appealing.

With this method, frac hits are detected earlier, and can be quantified as to severity. Also, pumping equipment can be shutdown, and tubing isolated to prevent the ingress of frac fluids as described in the referenced SPE article.

Since this frac hit detection system needs A) the ability to shut down the pumping unit when a frac hit is detected, and B) knowledge of when the pumping unit is operating to correctly calculate the frac hit indicator, the frac hit detection algorithms have been built into a pumping unit shutdown annunciation system. This system providesfor local annunciation and reset, but also remote annunciation via any Scada system as well as an actionable webpage. (Internet of Things) This is valuable to many older wells on timeclock or RPC that do not have an annunciation system for devices like vibration switches, low or high flowline pressures, or high tank, separator, or enviro-pot levels. Tubing and casing pressure data is also cost effectively measured by this device, and collectedby the operator’s Scada system for other beneficial applications.

A review of common pumping unit shutdowns is incorporated in the presentation, as there is minimal uniformity across industry nor API standards for this. Shutdowns that do not require a fault reset, but will instead allow automatic restarting when clear are:

Local on-off switches

Timer or RPC

Facility ESD

Phase monitor

Shutdowns that require a reset to resume operation are:

Low Flowline Pressure (after starting time delay)

High Flowline Pressure

Enviro pot / High Tank / High Separator

Vibration- Requires additional manual device reset

Motor Overloads – Requires additional manual device reset