Unconventional condensate gas reservoir fluid replacement and flow state control downhole sampling method

Abstract

The invention discloses an unconventional condensate gas reservoir fluid replacement and flow state control downhole sampling method. The method comprises the following steps of (S1) closing a well, so that the formation pressure is recovered to be higher than the original formation pressure for 3 to 6 MPa; (S2) connecting and assembling a pressure and temperature and density monitoring pipe string; (S3) placing the monitoring pipe string in a designed sampling point through an oil pipe or a sleeve; (S4) completing pressure maintaining replacement of the volume of fluids retained in a wellborethrough small gas production discharge; (S5) taking out the pressure and temperature and density monitoring pipe string; (S6) connecting and assembling downhole samplers into a downhole monitoring sampling pipe string; (S7) setting the control time of a sampler valve clock, and placing the sampling pipe string in a sampling point through an oil pipe or a sleeve; (S8) controlling the flow state tobe converted into slug flow or stratified flow and annular mist flow through large gas production discharge; and (S9) opening and closing the samplers according to the set valve clock, so that downhole sampling is automatically completed, an original fresh fluid sample of the stratum is obtained, the downhole monitoring sampling pipe string is taken out, and the sample is transferred with pressure maintaining and heat preservation.

Description

technical field [0001] The invention relates to the technical field of oil and gas reservoir sampling, in particular to an unconventional condensate gas reservoir fluid replacement and flow state control downhole sampling method. Background technique [0002] For the exploration and development of oil and gas wells that have obtained industrial oil and gas flow, it is of great significance to obtain fluid samples representing the original state of the reservoir, further test the properties of oil and gas reservoir fluids, judge the type of oil and gas reservoir fluids, and formulate development plans. [0003] The current fluid sampling methods in oil and gas reservoirs are mainly divided into surface sampling and downhole sampling. Sampling on the ground requires accurate measurement of oil and gas velocity, temperature and other data in the separator, and compounding in the laboratory according to the gas-oil ratio to obtain the fluid composition of the well fluid. Surfac...

AI Technical Summary

Problems solved by technology

Because this type of well adopts large-scale water injection fracturing technology, shutting down the well before sampling makes the formation pressure return to above the original formation pressure (making it possible to sample with water injection and pressure maintenance), resulting in the precipitation of Part of the condensate oil is evaporated back into gaseous state, and the condensate gas around the downhole sampling point is not really fresh original formation fluid due to the gravity differentiation and convection diffusion of condensate oil and gas in the wellbore and near-wellbore formations.

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