Infra-red Water Cut Meter Field Trial under Transient Conditions

Abstract

Determination of water and sediment content is required to measure accurately net volumes of actual oil in sales, taxation, exchanges, production allocation and custody transfer. Individual well testing is the most common practice for production allocation in gathering stations; nevertheless some operators tend to collect manual-samples to verify well production. However taking representative manual-samples under transient flow conditions represents a challenge. Therefore a technology capable of providing an accurate water measurement under such conditions is of high importance in the Oil and Gas industry. An oil operation Abu Dhabi based company selected a Near Infra Red (NIR) water cut meter for a field trial to evaluate its capabilities of measuring the full range of water cut (0-100%) under transient flow conditions. The evaluation program was conceived to compare the real-time measurement from the NIR water cut meter with concurrent manual sampling drawn for different wells. 24 hours test were run on 12 wells and a total of 48 samples were collected. Throughout the entire duration of the project, the NIR water cut meter was used along with a turbine flow meter and a Net Oil Computer (NOC). The NOC performed timed well tests integrating flow rate along with instantaneous water cut reporting, Net Oil and Net Water. The NIR water cut meter was installed in the liquid leg of a converted three-to-two phase separator operating under transient flow conditions (batch mode), as there were constant changes in flow rates and separator liquid level. It was determined that this condition made the water cut downstream of the separator unstable being a challenge to synchronize the manual samples result with the NIR water cut meter readings. Based on the success criteria, the NIR water cut meter evaluation was qualified as successful. The instrument proved to be within +/− 2% range of accuracy on water cut percentage measurement with a confidence level of 88%. And since true water production from a producing well, in many cases, cannot be determined by a single sample as wells tend to produce varying levels of water during the course of the day. The combination of NIR water cut meter with NOC proved to be a much more accurate instrumentation system for well production determination. This paper presents data obtained from multiple test stages. The well tests spanned the full range of water cut (0-100 %) on flow with transient conditions. The results showed successful water cut measurement uncertainty with dump cycle flow.

Water-Cut Measurement Techniques in Oil Production and Processing—A Review

“…The infrared water-cut meters rely on Near-Infrared (NIR) absorption spectroscopy. This water-cut meter can measure the water cut for the full range (0-100%) in transient conditions [29]. It is based on the large difference between the absorption of infrared radiation by crude oil and water [30].…”

Study of hysteresis effects and emulsion properties in watercut measurement using high speed multi-frequency impedance sensor

“…In the watercut meter industry, different methods have been in use such as near-infrared technique (NIR) [12], microwave method [13][14][15], gamma tomography [16], and impedance measurements [17]. The impedance measurement method uses the impedance variation of the oil-water mixture for different water contents to obtain the watercut.…”