Shale fluid-retaining closed coring device and method

Abstract

The invention discloses a shale fluid-retaining closed coring device and method. The shale fluid-retaining closed coring device comprises a coring drill bit, an outer cylinder and a drill rod joint which are connected in sequence, wherein the drill rod joint can drive the outer cylinder and the coring drill bit to rotate; a ball valve assembly, an inner cylinder, a plurality of fluid collecting tanks connected in series and a measurement-while-drilling device are connected in sequence and are arranged in the outer cylinder; the plurality of fluid collecting tanks are used for collecting natural gas in a rock core; the measurement-while-drilling device is used for measuring the temperature and pressure of the natural gas in the fluid collecting tanks; the shale fluid-retaining closed coringdevice further comprises a suspension assembly, one end of the suspension assembly is connected with the outer cylinder, and the other end of the suspension assembly is connected with the measurement-while-drilling device, the plurality of fluid collecting tanks and the inner cylinder, so that when the outer cylinder rotates, the inner cylinder does not rotate. When the core is taken and the drill is lifted, the ball valve assembly is closed, and the gas in the fluid collecting tanks is not lost, so that the shale sample and the lost gas content of the closed coring can be effectively obtained, the reliability and economic evaluation of the shale gas content and the shale gas reservoir reserve are improved, and the requirements of scientific research and production are met.

Description

technical field [0001] The invention belongs to the technical field of shale gas exploration and development, and more specifically relates to a shale fluid-preserving sealed coring device and method. Background technique [0002] Shale gas content is an important parameter for resource evaluation and area selection evaluation, and is also an important indicator of whether shale has industrial value and economic benefits. Accurately calculating the size of gas reserves is of great significance for deploying development plans. The gas content of shale is usually obtained by on-site desorption. All the free gas escapes, and the adsorbed gas is partially desorbed. Usually, the on-site desorption gas content consists of three parts: desorbed gas, lost gas and residual gas. The desorbed gas is calculated by desorption of the core, and the residual gas is obtained by crushing the core. The research on these two points has basically reached a consensus, and there are few objections...

AI Technical Summary

Problems solved by technology

However, the commonly used pressure-holding sealed coring technology is not suitable for shale gas (especially the sealed coring of deep high-temperature and high-pressure shale gas), so there is currently no closed coring device and Related engineering tests

[0004] The current technology mainly has the following deficiencies: (1) Although the temperature and pressure of conventional oil and gas closed coring can meet the requirements of shale gas, due to the existence of shale gas adsorption and occurrence, the temperature and pressure drop during drilling The resulting desorption of shale gas is inevitable, and a large amount of natural gas will be desorbed when the temperature is slightly lowered, and accidents such as pressure suppression and blasting will be caused if the temperature is slightly lowered. When the coring tool reaches the wellhead, remove the pressure cap on the joint of the blowout pipe, connect the blowout pipe, loosen the needle valve, and the pressure of the inner cylinder can be released, which avoids the pressure of the inner cylinder caused by core blockage and the occurrence of core damage. Shot blasting is not suitable for fluid-preserving sealed coring of shale gas; (2) Sealed coring devices for coalbed methane and methane hydrate are mostly used when the formation temperature and formation pressure are not high (coalbed methane: 10~ 20Mpa, 20~60℃; methane hydrate: 1~10Mpa, -10~28℃), which is significantly lower than deep shale gas 50~100Mpa, temperature 60~120℃, and is not suitable for the sealing of shale gas coring

Therefore, there is currently no example of application to high-temperature and high-pressure shale gas sealed coring

Images