A Novel, Highly Accurate and Innovative Headspace Depletion Protocol for the Ubiquitous Field Based H2S Scavenger Bottle Test Methodology for Sour Fluids

The field test evaluation of H2S scavengers in both sour produced water and sour crude has typically been carried out by evaluating changes in the H2S concentration of the headspace in the ubiquitous prescription bottle, used most frequently to screen emulsion breakers. This test method is not defined or regulated in any way and there are many undefined variables. Gas indicator tubes have typically been used to quantify the head space but suffer from inconvenience, inaccuracies, user dependency and high cost to name but a few. Sampling the gas head space is currently impossible without opening the space to the atmosphere. Unfortunately, this method currently requires opening the closed system to dilution and loss of H2S making it inherently inaccurate. Further this test takes a significant amount of time and thus in a series of many bottles, the last in line has a significantly longer chemical contact time than the first. A sour fluid is poured up to approx. half the bottle volume. Various scavengers are dosed into the bottle. The head space is then sampled and compared with a blank. The bigger the drop in headspace H2S concentration the better the scavenger is deemed to perform. In this paper we present a new rapid, accurate method to determine the H2S concentration in the headspace without opening it to the atmosphere. It involves the use of an innovative and recently designed self-contained, portable electronic monitor with internal sampling pump. This unit borrows from an original design which was a passive monitor which required a positive gas feed to measure the H2S concentration in a gas stream. This new monitor can sample a static head space such as a storage tank or in this case the head space of a prescription bottle test sample. The test takes approx. 10 seconds and eliminates the need for a prolonged delay, which eliminates contact time variability when testing multiple bottles. It also eliminates the inherent variability caused by technique of gas tubes from user to user. Real world data will be presented and compared with the conventional method of gas tubes. The superiority of this method will be immediately apparent, and it will greatly enhance the accuracy, test time and financial efficiency of this ubiquitous and industry standard method to evaluate H2S mitigation agents in the field. This novel method offers enormous benefits; speed, accuracy, cost effectiveness to name but a few. It could potentially revolutionize this universal method used to evaluate scavenger performance in both sour produced water and crude oil.