Preparation And Performance Of Guar Gum-based MEG Gel For Subsea Spool & Jumper Pipeline

In recent years,with the depletion of onshore and offshore oil & gas resources,the development of oil & gas fields has gradually moved from offshore to deepsea.Subsea production system is the main development mode of deepsea oil & gas fields.Deepsea spool & jumper pipe is the indispensable link to build a complete subsea production system.In the environment of low temperature and high pressure on the sea floor,wet natural gas is liable to form natural gas hydrate(NGH).The accumulation of NGH can cause pipeline blockage.Therefore,it is particularly important to develop the technology of injecting MEG gel in the spool & jumper pipe,which is mainly monopolized by foreign companies such as Beck-Hughes.Mastering this technology is conducive to the localization of subsea platform equipment in China.In this paper,the preparation and properties of guar gum based MEG gel were studied with reference to the preparation method of fracturing fluid.The main contents are as follows:(1)Using guar gum and its derivatives as thickener,the effect of MEG on the viscosity of guar gum and its derivatives was studied.The changes of intrinsic viscosity,interaction parameters and apparent viscosity with MEG were measured.The results showed that the glycol solution had a great effect on the viscosity of guar gum.The viscosity changes of hydroxypropyl guar gum(HPG)and carboxymethyl hydroxypropyl guar gum(CMHPG)at different shear rates and p H values were further explored.The thickening agents suitable for MEG gels were HPG and CMHPG.(2)The effects of each component of the gel on the gel properties were studied.It was found that MEG could weaken the crosslinking strength of the gel.Organic boron crosslinking agent was further prepared to reduce the influence of MEG.The formula of the MEG gel was determined as follows: the amount of CMHPG powder added was 1 wt%,the crosslinking p H was 7,and the amount of organic boron added was 9vol%.The prepared MEG gel had good thixotropic properties,temperature resistance and salt resisitance..(3)Various MEG gel breakers were screened and evaluated.The results showed that the breakers with softening effect were common mannanase,fumaric acid and glycolic acid.The breakers with viscosity reducing effect were common mannanaseand glycolic acid.Further testing the comprehensive properties of the breaker showed that mixed breaker had the best gel breaking performance for MEG gel.The formula of the mixed breaker is as follows: the amount of fumaric acid is 0.9 wt%,and the amount of enzyme is 0.6 wt%.(4)Based on the laboratory results,a pilot scale test of MEG gel was carried out.The preparation and injection process of MEG gel were designed.And the pilot plant was selected and installed.The feasibility of the experimental formula,injection process and equipment installation was verified.Through the practice of engineering application,experience had been gained in the MEG gel injection process for subsea spool & jumper pipe application.