| CPC E21B 47/10 (2013.01) [E21B 2200/20 (2020.05)] | 1 Claim |
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1. An experimental device for co-existence of overflow and lost circulation in a fractured formation during drilling of a deviated well, comprising:
a simulated deviated wellbore unit;
a computer data processing system;
a simulated formation fracture unit;
a gas injection system; and
a liquid injection system;
wherein the simulated deviated wellbore unit comprises an outer pipe, an inner pipe, a joint, a drill bit, a mixture outlet, an upper overflow port, a leakage port, and a lower overflow port; an inner cavity of the outer pipe is provided with the inner pipe to form a deviated casing; the joint is arranged at an upper end of the outer pipe and an upper end of the inner pipe; a lower end of the inner pipe is provided with the drill bit; a lower end of the outer pipe is provided with a plug; an upper side of the outer pipe is provided with the mixture outlet; a middle and lower side of the outer pipe is provided with the leakage port; and a middle of the outer pipe is provided with the upper overflow port and the lower overflow port;
the simulated formation fracture unit comprises a support block, a sealing gasket, a first liquid flowmeter, a lost liquid collection tank, two clamp plates, a fracture model, and a bolt; the two clamp plates are connected through the bolt and the support block, and a gap is formed between the two clamp plates; the bolt and the support block are configured to be adjusted to change a width of the gap; the fracture model is provided in the gap, and a plurality of fractures are provided in the fracture model; the sealing gasket is provided between an upper surface of the fracture model and each of the two clamp plates; an upper side of each of the two clamp plates is provided with a first pipeline and a second pipeline; the first pipeline is connected to the lost liquid collection tank through the first liquid flowmeter, and the second pipeline is connected to the leakage port through a first back pressure valve; and an inner end of the first pipeline and an inner end of the second pipeline are respectively communicated with the plurality of fractures in the fracture model;
the gas injection system comprises an air compressor and a gas flowmeter; and an outlet end of the air compressor is connected to the upper overflow port and the lower overflow port through the gas flowmeter and a third pipeline;
the liquid injection system comprises a liquid storage tank, a water pump, a second liquid flowmeter, and a liquid regulating valve; the joint is connected with a water inlet elbow through a fourth pipeline; a top of the liquid storage tank is provided with a first connection port for liquid discharge, and a bottom of the liquid storage tank is provided with a second connection port for liquid injection; the first connection port is connected to the joint through the water pump, the second liquid flowmeter, and the liquid regulating valve; and the second connection port is connected to the mixture outlet through a gas-liquid separator;
the fracture model comprises a model shell, the plurality of fractures, a liquid outlet, a liquid inlet, and a communicating groove; the model shell has a cuboid structure, and each of the plurality of fractures is strip-shaped; an inner cavity of the fracture model is provided with the plurality of fractures and the communicating groove perpendicularly connected with the plurality of fractures; an upper wall of the model shell is provided with the liquid outlet and the liquid inlet, and the liquid outlet and the liquid inlet are respectively connected with the communicating groove;
the plurality of fractures each have a width of 1 mm, 3 mm or 5 mm; and the number of the plurality of fractures is 5, 10 or 20;
an outer wall of a fifth pipeline connected with the liquid outlet and an outer wall of a sixth pipeline connected with the liquid inlet are respectively provided with a pressure gauge;
an annular space formed between the outer pipe and the inner pipe is provided with a pressure sensor, and the pressure sensor is connected to a computer system through a signal wire;
an upper part of the joint is provided with the water inlet elbow; a lower end of the water inlet elbow is communicated with the inner pipe, and an upper end of the water inlet elbow is connected to the liquid regulating valve;
an outlet end of the gas flowmeter of the air injection system is configured to be divided into two branches; one of the two branches is connected to the upper overflow port through a second back pressure valve, and the other of the two branches is connected to the lower overflow port through a third back pressure valve; and
the experimental device is configured to be operated through steps of:
(S1) opening the liquid regulating valve, and starting the water pump, so that water is pressurized by the water pump to successively fill a liquid injection pipeline, enter the inner pipe through the water inlet elbow, flow downward along the inner pipe to reach the drill bit, flow from bottom to top in the annular space formed between the outer pipe and the inner pipe, and flow out of the mixture outlet; and delivering an outflow from the mixture outlet to the gas-liquid separator for gas-liquid separation, wherein water is returned to the liquid storage tank for recycling;
(S2) after a flow pattern change in the liquid injection pipeline and a pressure change of the pressure sensor read by the computer system become stable, starting the air compressor and opening the first back pressure valve connected with the leakage port, so that gas, from the air compressor, sequentially flows through the gas flowmeter, the second back pressure valve, and the upper overflow port to enter the annular space between the outer pipe and the inner pipe, so as to simulate an overflow situation occurring on an upper side of a formation; or the gas sequentially flows through the gas flowmeter, the third back pressure valve, and the lower overflow port to enter the annular space between the outer pipe and the inner pipe, so as to simulate an overflow situation occurring on a lower side of the formation;
(S3) opening the first back pressure valve connected with the leakage port to allow a fluid in the annular space to enter the simulated formation fracture unit; wherein a type of the fracture model, the number of the plurality of fractures and width of the plurality of fractures are determined according to simulation needs, so as to simulate lost circulation situation in the formation under different fracture conditions; and the fluid eventually flows into the lost liquid collection tank;
(S4) opening the first back pressure valve, closing the second back pressure valve connected with the upper overflow port, and opening the third back pressure valve connected with the lower overflow port, so that the gas flows out of the lower overflow port to simulate a wellbore flow law and a formation lost circulation law under the co-existence of overflow and lost circulation in an upper lost circulation-lower overflow pattern;
(S5) opening the first back pressure valve, the second back pressure valve, and the third back pressure valve, such that the gas flows out from the upper overflow port and the lower overflow port, and leaks through the leakage port; obtaining, by the computer system, readings of the first liquid flowmeter, the second liquid flowmeter, the gas flowmeter, the pressure gauge, the first back pressure valve and the second back pressure valve, and analyzing a flow law and a formation lost circulation law under the co-existence of upper and lower overflow and lost circulation; and
(S6) adjusting openings of the first back pressure valve, the second back pressure valve, and the third back pressure valve to simulate a flow law under the co-existence of overflow and lost circulation in different formation conditions; changing inclined angles of the outer pipe and the inner pipe and repeating the above steps to simulate a law of co-existence of overflow and lost circulation in wells with different inclined angles.
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