Drilling fluids are critical to success in horizontal directional drilling applications, while biocides is the most important part for high efficiency, to kill bacteria, algae in water and also kills fungi. 

   Many oilfield drilling service companies in the US and Canada use Xanthan gum, THPS biocide and Curdlan gum in the water flooding process. Here is a course drafted by Dr. Georgy Zerkalov from Stanford University:

·Water Flooding

Tetrakis(hydroxymethyl) phosphonium sulfate (THPS) should be added to a water injection system when uniform mixing is needed.

First step: add 93 -350 ppm biocide THPS for a noticeably fouled system. When added to a flowing system, slug dose for 2 -6 hours based on flow rates. Repeat as necessary until control is achieved.

Second step: once control has been achieved. Add 14 -98 ppm THPS biocide weekly or as needed to maintain control. As for continuous treatment, THPS can be dosed continuously at a level of 14 -67 ppm.

·Oil and Gas Production and Transmission Systems and Pipeline

THPS 75% solution should be added at a point in the pipeline where uniform mixing will occur.

The criteria for the success of the treatment will be a reduction in the bacterial count and/or corrosion rates. Adding steps is the same as that of water injection. As for continuous treatment, tetrakis(hydroxymethyl) phosphonium sulfate can be dosed continuously with 14 -100 ppm dosage.

·Drilling Muds, Well Completion and Workover Fluids

Add 33-1400 ppm THPS 75% to a freshly prepared fluid depending on the severity of contamination.

·Gas Storage Well systems

Individual injection wells should be treated with THPS 75 at the same dosage and same steps as described underwater flooding.

Injections should be repeated as needed to maintain control.

Individual drips should be treated with a sufficient quantity of product to produce a concentration of 33.3 -133.3 ppm when diluted by the water present in the drip.

Injections should be repeated as needed to maintain control.

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