Chemical Injection Valves

• Chemical injection valves are used to place chemicals at a specific point in the downhole flow stream.

• The chemical may be supplied by either annular feed or dedicated line supply.

• The valves typically are placed in side pocket mandrels is the application is serviceable.

• The following slides highlight some failures that may help in designs.

8/25/2015 1 George E. King Engineering

GEKEngineering.com

CIV – Failure Points

• The primary failure for chemical injection valves is by plugging in the valve. The primary cause is chemical supply problems that allow solids or partially reacted chemicals to reach the valve. Filtering chemicals at the surface to less than the bridging level of the valve (1/7th of orifice minimum) is useful. Generally, filtering to 50 microns is adequate. However, some chemicals may react while going down the supply line and create larger particles and some chemicals such a scale inhibitors are low pH and may corrode the supply line or form corrosion by-products. To minimize problems the behavior of the injected chemicals to the supply metallurgy, the valve and the well flow stream should be understood.

8/25/2015 2 George E. King Engineering

GEKEngineering.com

CIV – Failure Points

• A secondary failure mechanism for chemical injection valve failures is ball and seat cracking in the valve. Chemical injection valves are essentially throttling valves and are either open or closed. The impact of opening and closing will create the opportunity for breaks. A longer lasting valve is to use a double check orifice valve instead of a ball and seat valve. The double check orifice is also more beneficial where the injected chemical is normally at a lower pressure than the flowing fluid in the tubing. The double check orifice only dispenses fluid into the tubing when the chemical supply pump is engaged. This is particularly useful for intermittent treating.

8/25/2015 3 George E. King Engineering

GEKEngineering.com

CIV – Failure Points

• Supply line plugging is the third common failure mechanism. Plugging potential is a direct function of supply line diameter and is also related to particles in the injected chemical as described in #1. Nominal diameter lines of ½” are much less prone to plugging by normal particles than lines of ¼” or less. Plugs may form in lines from agglomeration of small particles in the fluid or from dehydration of particles at the site of a seepage leak. Both occurrences have been noted.

8/25/2015 4 George E. King Engineering

GEKEngineering.com

CIV Failure Points

• Crushing of the supply lines is a problem during pipe running and partially collapsed lines may lead to an increased risk of plugging. Effective coupling protectors appear to reduce incidence of line crushing as proven by similar line function for downhole valves. Leaks in the supply lines are caused by internal or external corrosion. Metallurgy should be examined from both respects.

8/25/2015 5

George E. King Engineering GEKEngineering.com

CIV – Failure Points

• Side pocket mandrel failure is very low. Only one collapse (treating pressure associated) and a few leaks due to corrosion could be documented. Several cases or pocket scaling and scratching very found, but typically in very old completions.

8/25/2015 6 George E. King Engineering

GEKEngineering.com

CIV Failure Frequency

Equipment Failure

Frequency,

failures per

well per

year

Approx.

Failures %

of

application

s per year

Comments/Source

Chemical Injection

Valves, ball and seat

type

0.10 10% Weatherford, Rick

Seagraves

Double Check Orifice

Valves

0.01 1% Weatherford, Rick

Seagraves

Line Plugging 0.002 <<1% Literature

estimation

Line Crushing or Leaks 0.009 1% BP failures data

base

8/25/2015 7 George E. King Engineering

GEKEngineering.com