Kinetic Hydrate Inhibitors - Sensitivity towards Pressure and Corrosion Inhibitors

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractReplacement of the traditional thermodynamic hydrate inhibitors (methanol and glycols) in wet gas applications is more and more highly desirable for cost savings and for Health, Safety & Environment (HSE) considerations. This seems achievable by using alternative Kinetic Hydrate Inhibitors (KHI). KHIs are able to delay hydrate formation for the time needed to transport the effluents in hydrate region conditions. The KHI efficiency is generally based both on the subcooling that can be matched by the inhibitor and on the hydrate formation time delay that the inhibitor can provide. Within the frame of various Field Development studies carried out since 1990, we have had the opportunity to evaluate the performance of several KHIs. These evaluations have been conducted on two hydrate loop facilities with a service pressure of respectively 80 bara and 165 bara. Thanks to these two pilots, we have been able to observe and to quantify the influence of various parameters on the KHI efficiency. Among these parameters, two of them have proved to be of importance: the presence of other inhibitors, such as corrosion inhibitors (CI), and the operating pressure. Their strong influence is illustrated in this paper through the results obtained in three different case studies. The practical conclusion is that KHIs selected in "routine" lab tests may be not efficient in the field and that appropriate selection tests are required.

An investigation into the kinetic hydrate inhibitor properties of two imidazolium-based ionic liquids on Structure II gas hydrate

“…KHIs delay the nucleation and usually also the crystal growth of gas hydrates. The nucleation delay time (induction time), which is the most critical factor for field operations, is dependent on the subcooling (DT) and pressure in the system as well as other factors such as the type of oil or condensate or the presence of other production chemicals such as certain corrosion inhibitors Arjmandi et al, 2005;Peytavy et al, 2007;Kelland et al, 2008).…”

Selection of Commercial Kinetic Hydrate Inhibitors Using a New Crystal Growth Inhibition Approach Highlighting Major Differences Between Them

“…We would continue meanwhile applying the Second Germination (SG) procedure with our flow loops for such checks [7,8]. But as the 8°C subcooling from the s-II boundary is within their SGR(S) and not inside their SGR(VS), cocktails 1 & 9 are out.…”

“…operating outside their thermodynamic P&T envelope. In order to avoid this poor reproducibility of LDHI-KHIs tests, TOTAL developed a specific lab procedure termed "second germination" (SG) first applied in our hydrate flow loops devices [7,8] then later applied in autoclave cells [9][10][11]. In order to try to develop new Oil&Gas fields which are now discovered in more and more harsh environments, the production inside the hydrate P&T thermodynamic zone has started to be considered.…”

“…The development of LDHIs has been subjected to a lot of research works for the last twenty years and to several field testing and deployments for the last fifteen years [1,2]. It has been found that particularly corrosion inhibitors (CI) can sometimes be very detrimental to their efficiency [7]. vs. water): the required concentration for these additives is usually in the range of 0.5 to 3 wt% vs. water.…”

Successful Field Application of an Inhibitor Concentration Detection System in Optimising the Kinetic Hydrate Inhibitor (KHI) Injection Rates and Reducing the Risks Associated with Hydrate Blockage

“…Other factors have been shown to potentially affect the KHI efficiency, one of the main being interactions with corrosion inhibitors [2][3] . % versus the water rate.…”