A Downhole Sampling Method for Fluid Displacement and Flow State Control in Unconventional Gas Condensate Reservoirs

Abstract

The invention discloses an unconventional condensate gas reservoir fluid replacement and flow state control downhole sampling method, comprising the following steps: S1: shutting down the well to restore the formation pressure to 3-6 MPa higher than the original formation pressure; S2: connecting and assembling the pressure , temperature and density monitoring pipe strings; S3: lower the monitoring pipe strings to the designed sampling point through the tubing or casing; S4: use small gas production to blow out and complete the replacement of the retained fluid volume in the wellbore with pressure; S5: take out the pressure, temperature and Density monitoring pipe string; S6: Connect and assemble the downhole sampler into a downhole monitoring sampling pipe string; S7: Set the clock control time of the sampler valve, run the sampling pipe string to the sampling point through the tubing or casing; S8: Use a relatively Large gas production blowout control flow state changes to slug flow or stratified flow and annular mist flow; S9: The sampler automatically completes downhole sampling according to the set valve clock opening and closing, obtains the original fresh fluid sample of the formation, and takes out the downhole monitoring sampling pipe string, and carry out pressure-holding and heat-preservation transfer.

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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