CN104237101A - Bridge imitation and flow measurement avoidance type cross rock core permeability measurement method and device - Google Patents

Abstract

The invention discloses an imitation electric bridge measurement-free type rock core permeability step-level measuring device and a measuring method thereof. Among them, the disclosed measurement device requires four core holders and a differential pressure gauge, and the four core holders and a differential pressure gauge are assembled through multiple conduits and four tees in the manner of a Wheatstone bridge. The disclosed measurement method is divided into four steps. The first step is to select standard rock cores for the core holders on the two proportional arms and the core holder on the comparison arm; the second step is to carry out displacement experiments, including assembling the measurement device, for The core holder is installed with the core, and the ring pressure and the pressure pump are pressed; the third step is to adjust the permeability of the standard core in the core holder on the comparison arm, so that the pointer of the differential pressure gauge points to zero; the fourth step is to perform data processing, and the measured The relevant data are substituted into the specified data formula to calculate the permeability of the core to be tested. Compared with the traditional steady-state flow method of measuring the permeability of the core, this technology can realize the measurement of the permeability of the core without measuring the flow rate.

Description

Method and device for cross-level measurement of rock core permeability without measuring flow by imitation bridge

technical field

The invention relates to a permeability measurement technology, in particular to a bridge-like bridge-free measurement-free type rock core permeability cross-level measurement device and a bridge-imitation flow-free measurement-free rock core permeability step-level measurement method. the

Background technique

In the traditional steady-state flow method to measure the core permeability experiment, the accurate measurement of the flow rate is often difficult, especially in the process of low-permeability, ultra-low-permeability, and tight core displacement experiments, or when the displacement environment is relatively harsh. Measurement accuracy is even more difficult to guarantee, and sometimes even impossible to measure, resulting in large errors or inability to measure parameters such as core permeability. For example, when measuring the permeability of tight reservoir rocks, the liquid flow rate is very small. For a standard core with a permeability of 1×10 ^-3 μm ² , the flow rate is only about 0.8ml/min when the displacement pressure is as high as 40MPa (assuming that the liquid distilled water); when the core permeability is lower, the flow rate will be even smaller. The current general-purpose flowmeters, such as electromagnetic flowmeters, turbine flowmeters, mass flowmeters, etc., cannot be applied due to their large measuring ranges. Another example is high temperature and high pressure, especially the existence of high temperature, so that the expelled fluid has gas-liquid two-phase during the core displacement process. At present, the expelled fluid is mostly directly measured by an open small measuring cylinder, so that the capture and measurement of the gas phase cannot be realized; In addition, at high temperature, the liquid is volatile, so the measurement error of the liquid is relatively large.

The core displacement experimental device for measuring the core permeability, such as the FS-II overburden pressure porosity tester, generally consists of a single core holder, a pressure pump, a pressure gauge, and pipe valves, and these core displacement experiments The devices all include a metering system, that is, various flow meters. the

The final measurement object of the core displacement experiment is the permeability, and the fluid flow rate is only an intermediate measurement of physical quantities. As the current flow measurement problems are difficult to solve, how to realize the measurement of the permeability under the premise of avoiding the measurement of the fluid flow rate and ensure a certain The measurement accuracy is a problem to be solved by those skilled in the art. the

Contents of the invention

The object of the present invention is to provide a rock core permeability measurement device, which can realize the measurement of rock core permeability without measuring the fluid flow rate, and can guarantee a certain measurement accuracy. On the basis of providing the above-mentioned rock core permeability measuring device, a rock core permeability measuring method is also provided. the

The cross-level measurement device for flow-free rock core permeability imitation bridge provided by the present invention includes a pressure pump for injecting displacement fluid into the core holder, a differential pressure gauge for indicating whether the pressures at the two points to be measured are balanced, and a Containers for collecting drive-off fluids, four core holders, four tees and multiple conduits to connect the above parts. Among them, four core holders and a differential pressure gauge are connected through a tee and a conduit in the manner of a Wheatstone bridge, and a standard core with known permeability is placed in the core holders on the two proportional arms, and the comparison arm The permeability of the standard core in the core holder on the upper arm is adjustable, the core holder on the measuring arm is used to place the core to be tested, and the differential pressure gauge is connected to the "bridge" through a conduit. The pressure pump is connected to one end of the second diagonal line (not the "bridge" road) through a conduit, and the collection container is connected to the other end of the second diagonal line through a conduit. the

The present invention also provides a method for measuring the cross-level measurement of rock core permeability without measuring the flow rate of an imitation electric bridge: firstly, according to the estimated value of the rock core permeability to be measured, the rock core holder on the two proportional arms and the rock core holder on the comparison arm Then, the measuring device is assembled according to the Wheatstone bridge, and the four cores are respectively placed in the four core holders, and the ring pressure is applied, and the pressure pump is turned on to pressurize, and the displacement experiment is carried out, and the driven fluid flows into the collection Container; during the displacement process, constantly adjust the permeability of the standard core in the core holder on the comparison arm, so that the pointer of the differential pressure gauge points to zero, that is, the pressures at the two points to be measured are balanced; finally, the core holder on the comparison arm is balanced The permeability of the core in the holder, and the permeability of the core in the core holder on the two proportional arms are substituted into the formula to calculate the permeability of the core to be tested. the

It is preferable that the three cores on the two scale arms and the comparison arm are moderately permeable sandstones with high permeability measurement accuracy, and the permeability ranges from 50 to 500×10 ^-3 μm ² .

Preferably, the permeability of the built-in core is changed by adjusting the confining pressure of the core holder on the comparison arm. the

Description of drawings

Fig. 1 is the structural representation of the bridge-free measurement-free flow type rock core permeability step-by-step measuring device of the present invention; (see Fig. 1)

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

In the first embodiment, it is assumed that the geometric shape and size of the three standard cores and the cores to be tested are exactly the same, and the four cores are medium-permeable sandstones, and their permeability ranges from 50 to 500×10 ^-3 μm ² , further Assuming that the permeability of the core in the core holder 4 on the proportional arm parallel to the measuring arm is K ₁ , and the permeability of the core in the core holder 5 on the proportional arm parallel to the comparison arm is K ₂ , the permeability of the core to be measured is The permeability is K _X , and when the pointer of the differential pressure gauge 7 points to zero, the permeability of the core in the core holder 9 on the comparison arm is K ₃ . According to Darcy's law, the relationship between the permeability of the four cores can be deduced as: K _X = (K ₂ /K ₁ )K ₃ , the formula shows that when the pointer of the differential pressure gauge 7 points to zero, that is, the differential pressure gauge 7 When the pressure at both ends reaches equilibrium, the permeability K _X of the core to be tested can be calculated by knowing the permeability K ₁ , K ₂ , and K ₃ of the three standard cores.

The specific measurement process of the permeability K _X of the rock core to be tested is as follows:

Step 1: Select two medium-permeable sandstones with equal permeability (K ₁ =K ₂ ) as the standard cores in the core holders 4 and 5 on the two proportional arms, and select the permeability to be equal to the permeability K ₃ of the core to be tested The medium-permeable sandstone is used as the standard rock core in the rock core holder 9 on the comparison arm;

Step 2: Combine four core holders 4, 5, 9, 10 and a differential pressure gauge 7 using multiple conduits 2 and four tees 3, 6, 8, 11 in the manner of a Wheatstone bridge , and further connect the differential pressure gauge 7 to the "bridge" through the conduit 2, connect the pressure pump 1 to one end of the second diagonal line, and connect the collection container 12 to the other end of the second diagonal line, thus forming The bridge-free measuring flow type rock core permeability step-level measuring device is used, and then four rock cores are respectively placed in four rock core holders 4, 5, 9, 10, and the four rock core holders 4, 5, 9, 10 add ring pressure, turn on the pressure pump 1 to pressurize, carry out the displacement experiment, and drive the fluid into the collection container 12;

Step 3: Constantly adjust the confining pressure of the core holder 9 on the comparison arm, and then change the permeability of the built-in core, so that the pointer of the differential pressure gauge 7 points to zero, that is, the pressure at the two points to be measured reaches a balance;

Step 4: Substitute the core permeability K ₃ in the core holder 9 on the comparative arm and the core permeability K ₁ and K ₂ in the core holders 4 and 5 on the two proportional arms into the formula K _X =(K ₂ /K ₁ )K ₃ , the permeability K _X of the core to be tested is calculated.

In the second embodiment, except that the core to be tested is assumed to be a low-permeability core (permeability ranges from 10 to 50×10 ^-3 μm ² ), other assumptions are the same as those in the first embodiment. When the pointer of the differential pressure gauge 7 points to zero, the relationship K _X = (K ₂ /K ₁ ) K ₃ among the four core permeability still holds true. At this time, the specific process of measuring the permeability K _X of the core to be tested and the Similar in one embodiment, the difference is that in step 1, the permeability of the medium-permeable sandstone selected in the core holders 4 and 5 on the two proportional arms is no longer equal, and the ratio of the two permeability K ₂ /K ₁ is between 0.1 and 0.5, and further assuming that the permeability of the medium-permeability sandstone in the core holder 9 is 100×10 ^-3 μm ² , the permeability K ₁ and K ₂ and K ₃ into the formula K _X = (K ₂ /K ₁ )K ₃ , the calculated permeability of the core to be tested is between 10 and 50×10 ^-3 μm ² , indicating that the core to be tested is of low permeability This shows that this technique can be used to measure the permeability of low-permeability cores by using medium-permeability sandstone with high permeability measurement accuracy.

Further analysis shows that when the ratio K ₂ /K ₁ of the medium permeability sandstone permeability selected in the core holders 4 and 5 on the two proportional arms is between 5 and 10, the formula K _X =(K ₂ / K ₁ ) K ₃ calculates that the permeability of the core to be tested is between 500 and 1000×10 ^-3 μm ² , which is a high permeability core.

It can be concluded that this technology can be used to measure the permeability of low-permeability cores and high-permeability cores by using medium-permeability sandstone with high permeability measurement accuracy, and the cross-level measurement of core permeability can be carried out. the

Claims (4)

1. A rock core permeability measurement device, comprising a pressure pump (1) for injecting displacement fluid into the core holder, a collection container (12) for collecting the displacement fluid, and multiple conduits (2) And four tees (3, 6, 8, 11), it is characterized in that, it also comprises four rock core holders (4, 5, 9, 10) that are used for built-in rock core, an indication two point pressures to be measured Balanced differential pressure gauge (7), four core holders (4, 5, 9, 10) and a differential pressure gauge (7) pass through multiple conduits (2) and four The tees (3, 6, 8, 11) are combined, and the standard rock cores with known permeability are placed in the rock core holders (4, 5) on the two proportional arms, and the rock core holders ( 9) A standard rock core with adjustable permeability is placed inside, the core holder (10) on the measuring arm is used to place the rock core to be tested, the differential pressure gauge (7) is connected to the "bridge" through the conduit (2), and the pressure The pump (1) is connected to one end of the second diagonal line through the conduit (2), and the collection container (12) is connected to the other end of the second diagonal line through the conduit (2). the 2. The rock core permeability measuring device according to claim 1, characterized in that the confining pressure of the rock core holder (9) on the comparison arm is adjustable. the 3. a method utilizing the rock core permeability measuring device claimed in claim 1 to measure the rock core permeability, is characterized in that, comprises the steps: Step 1: according to the estimated value of the rock core permeability to be measured is on the two proportional arms The rock core holder (4,5) and the rock core holder (9) on the comparison arm select the standard rock core; Step 2: assemble the rock core permeability measuring device described in claim 1, put four rock cores respectively in four rock core holders (4, 5, 9, 10), and add ring pressure, open the pressure pump (1 ) to pressurize, carry out the displacement experiment, and drive out the fluid to flow into the collection container (12); Step 3: Adjust the permeability of the standard core in the core holder (9) on the comparison arm so that the pointer of the differential pressure gauge (7) points to zero, that is, the pressure at the two points to be measured reaches a balance; Step 4: Substituting the core permeability in the core holder (9) on the comparison arm and the core permeability in the core holder (4, 5) on the two proportional arms into the formula to calculate the permeability of the core to be tested permeability. the 4. the method for measuring rock core permeability as claimed in claim 3, is characterized in that, in described step 3, changes the permeability of its built-in rock core by regulating the confining pressure of rock core holder (9) on comparison arm . the