TITLE:
Risk Analysis of Gas Hydrate Formation during Deepwater Gas Well Testing
AUTHORS:
Hongjun Yang, Liang Hao, Muwang Wu
KEYWORDS:
Risk Analysis, Deepwater, Gas Well, DST, Gas Hydrate
JOURNAL NAME:
International Journal of Geosciences,
Vol.7 No.9,
September
7,
2016
ABSTRACT: During deep-water gas
wells testing period, predicting the generating zone of hydrate precisely in
the whole flow range (bore holes and surface flow lines) is the key prerequisite
of guarantee for testing flow. The unusual deep-water environment and low gas
density make it easy to meet the conditions of hydrate generation during deep-water gas wells testing
period, such as low temperature and high pressure, especially under the testing
conditions, for instance, near mud line, surface chock line, low gas generating rate
and surface shut-in. Wherefore, in view of all the operational modes during
testing period (clean-out, variable rate flow, downhole and surface shut-in),
based on temperature field of the whole flow range and phase equilibrium condition of hydrate, predicting
method of hydrate generation zone is published; by taking enthalpy as the object of study, temperature
calculation model increases
the accuracy of temperature prediction; by integration of bore holes and
surface lines, predicting plate of hydrate generation in the whole flow range is
published. During flow period, the generating condition of hydrate is affected
by rate of flow, and the lower the rate of flow is, the wider the hydrate
generation zone is; during the stage of shut-in and initial flow, if pressure of
strings is higher and temperature is lower, risk of hydrate generation will be
greater and hydrate generation zone will be larger, so relevant actions should
be taken to restrain hydrate generation.