JP2796748B2 - Single hole fluctuating hydraulic permeability tester and test method - Google Patents

Description

The present invention relates to an apparatus and a method for testing the permeability of the ground, and more particularly, to a method using a single borehole in the ground to be investigated. The present invention relates to an apparatus and a method for examining the water permeability of the ground around a borehole by measuring the water permeability and the vertical propagation pressure.

[Prior art] As a technique for investigating the permeability and the stratum structure of the ground, various types of hydraulic water flows of varying type are supplied into a borehole, and the permeability and the structure of the ground are determined from the amount of water permeability and the propagation pressure at that time. There is something that seeks to obtain the knowledge of. In this survey, a plurality of boreholes are excavated in the survey target area, and the water permeability and propagation pressure between each other are obtained.

On the other hand, in the field of petroleum engineering, there is a technique for determining the permeability of an oil reservoir for oil reservoir evaluation. In this test, the inside of a production well that performs oil production is divided by a packer, pressure sensors are arranged above and below the division position, and pressure is applied to the upper part of the division position by stopping oil production or injecting fluid into the production section, Measure the pressure propagating to the lower part of the dividing section.
Using the pressure rise amount and the time delay of the pressure rise calculated from the test results, it is assumed that the transmission point and the reception point are homogeneous, and the horizontal and vertical directions of the oil reservoir are determined from the position of the impervious boundary known in advance. Is determined analytically.

[Problems to be Solved by the Invention] The method using a plurality of boreholes such as a transmission hole and a reception hole can investigate a wide range of water permeability and a stratum structure, but requires a large amount of equipment and work, and the analysis becomes complicated. There is a problem that costs and takes a lot of time.

In the field of petroleum engineering, in many cases, the oil layer is formed of porous rocks such as sandstone, so that it is possible to assume that the transmission point and the reception point are homogeneous. However, the ground treated in the general civil engineering field often shows a complicated stratum structure, and the above assumption is rarely satisfied. In addition, in the case of the oil reservoir evaluation method, the depth of the impermeable boundary is known in advance, but the impermeable boundary is not always present in general ground and the depth is often unknown until a test result is obtained. Further, the method of oil reservoir evaluation is to fix the transmission-reception depth on the structure of the test equipment in order to obtain the approximate permeability of the entire oil reservoir using the production well, In the general civil engineering field, it is required to understand the distribution of fine water permeability along the borehole. In the conventional method, since the transmission point and the reception point cannot be set arbitrarily, it is impossible to continuously know the distribution of water permeability. As described above, the conventional technique used for oil reservoir evaluation has a large difference between a formation in which oil is produced and a formation to be surveyed in the general civil engineering field, and although it seems that there is similarity, it cannot be applied as it is.

An object of the present invention is to solve the above-mentioned problems and to provide an apparatus and a method that can easily and economically perform a geological survey and a groundwater survey.

[Means for Solving the Problems] The present invention, which can achieve the above objects, measures the water permeability and the structure of the ground around the boring hole by measuring the vertical water permeability and propagation pressure in a single boring hole. It is an apparatus and a method for investigating.

The basic device includes three or more pneumatic pressure-blocking packers arranged in a line at intervals, pressure sensors provided in a plurality of packer sections formed by adjacent packers, and a device axial direction. And an irrigation channel having water permeability and opening only in any one packer section.

In order to actually perform the test, a variable water pressure generation / supply device connected to the water injection channel and a device for recording and analyzing signals from each pressure sensor are installed on the ground.

The method of the present invention uses the above-described apparatus, and after inflating the packer section, fluctuates with the passage of time of the flow rate in the transmission packer section where it is opened from the fluctuating water pressure generation / supply device through the water injection path, The response pressure in another receiving packer section is measured, and the horizontal and vertical permeability distributions of the ground distributed in the transmitting packer section and the receiving packer section are obtained.

[Action] When a predetermined flow rate of water is injected from the fluctuating water pressure generation / supply device on the ground into the transmission packer section cut off by the packer in the borehole of the ground to be tested, a pressure rise occurs in the ground due to the effect. , Water pressure changes in the receiving packer section. The interval between the sending packer section and the receiving packer section can be adjusted by the position of the packer, and a continuous and detailed permeability distribution can be obtained over the entire length of the test hole by moving the whole apparatus up and down along the boring hole.

In addition, the problem that the presence or depth of the impermeable boundary is not known in advance and the problem that the transmission point-reception point is not always uniform can be solved by using a numerical analysis method as an analysis method. That is, the analysis target area is divided concentrically in the horizontal plane, sliced in the axial direction and divided into a number of annular elements, and a permeation flow simulation for a three-dimensional axisymmetric gas-liquid two-phase flow is performed. Search for a permeability distribution model having horizontal and vertical permeability that most accurately reproduces the measurement results by inverse analysis with parameter correction. This will investigate the soil permeability and structure details along the borehole.

Embodiment FIG. 1 is an explanatory view showing one embodiment of a test apparatus according to the present invention. In this embodiment, four pneumatic pressure cut-off packers are used, the second packer section from the top is a transmission section (pressure applying section), and the upper and lower packer sections are a reception section (pressure measurement section). It is.

Four pneumatic pressure shut-off packers 10 are arranged in a line at a predetermined interval. The packer unit 10 includes a center pipe 12 and a flexible packer tube 14 that is coaxially located so as to surround the center pipe 12 and maintains airtightness. The center pipes 12 are connected by a connecting pipe 16 having a predetermined size. Here, the second packer section from the top and 3
Perforated water pipe 18 as a connecting pipe between the packer section of the stage
The inside is communicated with a center pipe and a connecting pipe above it so that water can be supplied from the upper end, and the lower end is closed so that water does not pass below it. Pressure sensor 20 for each packer section
Is provided. The signal lead wire 22 of the pressure sensor 20 extends upward through each packer portion, and each packer portion is connected in series by an air tube 24 for expanding the packer portion. The distance between adjacent packers can be freely changed by changing the length of the perforated water pipe 18 or the length of the connecting pipe 16. Each packer section 10 is simultaneously expanded by supplying pressurized air from the ground using the air tube 24, so that the inside of the hole can be blocked in each section.

FIG. 2 shows a schematic diagram of the water permeability test. A boring hole 32 is excavated in the ground 30 in the analysis target area. Then, a device as shown in FIG. 1 is inserted into the boring hole 32. A water supply passage extending from the upper part of the apparatus to the ground is provided, a variable water pressure generating / supplying apparatus 34 is connected to the water supply path, and each pressure sensor 20 is connected to a recording / analyzing apparatus 36 by a signal lead 22. Then, water having a clear change with time in the flow rate is injected from the variable water pressure generation / supply device 34 on the ground. Here, water is injected such that the water amount Q changes in a rectangular wave shape.

In addition, such a large amount of intermittent water injection is performed by a centrifugal pump, a return path adjustable between a discharge side and a suction side to keep the discharge pressure constant, and a needle opening / closing valve provided in a discharge pipe. By adjusting the flow rate in the return path and opening and closing the discharge pipe with the needle opening / closing piece.

Pressure is detected in each packer section. The signal indicates the time change of the received pressure P, and the measurement result is recorded and analyzed
Sent to 36 for analysis.

In these embodiments, four packer sections are used and three packer sections are set including the pressure applying section.
By using more packers, the time required for measurement can be reduced. At a minimum, three packer sections are used, and the packer section is provided at two places including the pressure applying section. In any case, by performing the test by shifting the insertion position in the depth direction of the borehole, the water permeability test can be performed over the entire borehole.

The measurement is performed by injecting a rectangular wave of water from a specific outgoing packer section (ie, injecting a certain amount of water for a certain time,
Next, the pressure in the transmission packer section and the pressure in the reception packer section due to the case where the injection blocking cycle is repeated a plurality of times) are measured and plotted at regular intervals.
The pressure in the outgoing packer section has a certain level due to the effect of water pressure at that depth. Further, the response pressure in the reception packer section is obtained as an increase / decrease value obtained by subtracting the hydrostatic pressure since the level differs depending on the depth. From these measurement results, the pressure transmission delay time and the response pressure are obtained.

The analysis is performed by constructing an axially symmetric cylindrical coordinate system model as shown in FIG. 3 in order to obtain the state around a single borehole. In other words, the area to be analyzed around the borehole is concentrically sliced at right angles to the axis, divided into a number of annular elements, and the permeation distribution using the horizontal and vertical permeability as parameters for each annular element. Build the model.
Then, a mass balance formula is established using the inflow and outflow of the three-dimensional axisymmetric gas-liquid two-phase permeate flow at each annular element as a boundary condition, and the response pressure in each of the receiving packer sections is numerically analyzed. This basic equation establishes a material balance equation for each of the two phases based on Darcy's law and a continuous equation. As a result, the material balance equation can be expressed as follows per unit volume.

Where k _r : permeability in the horizontal direction k _z : permeability in the vertical direction k _ra : relative permeability of air k _rw : relative permeability of water μ _a : viscosity coefficient of air μ _w : viscosity coefficient of water B _a : Air volume coefficient B _w : Water volume coefficient P _a : Air pressure P _w : Water pressure S _a : Air saturation S _w : Water saturation P _c : Capillary pressure γ: Fluid density h: Depth φ: Porosity of the ground Equation (1) is the mass balance equation for the gas phase, and equation (2) is the mass balance equation for the liquid phase. The above equation is discretized in space and time and analyzed. Here, since the interval between the transmitting point and the receiving point is constant over the entire length of the borehole, the calculation is performed using an annular element having a constant thickness. In the radial direction, several divisions are performed, and the outermost ring element located far enough away is operated so that the pressure is always constant for setting boundary conditions.

The analysis is repeated by the nonlinear least-squares method with the permeability in the horizontal direction and the permeability in the vertical direction during the forward analysis being unknown, and executed until the values converge. However, for simplicity as much as possible, the calculation is based on a model that annular elements having the same depth have the same horizontal and vertical permeability. Modify the permeability distribution model, and again 3
The response pressure in each receiving section is obtained by numerical analysis based on a material balance equation using the inflow and outflow of the two-dimensional symmetric gas-liquid permeation flow as boundary conditions. Such an operation is performed until convergence, and an optimal model is obtained. FIG. 4 shows an example of the actual measurement results. The above procedure is represented by a flowchart in the fifth section.
FIG.

Although the preferred embodiment of the present invention has been described in detail,
The present invention is not limited to only such a configuration. The water to be injected from the transmission packer section is not limited to a rectangular wave shape, and may have an arbitrary waveform as long as the change with time of the water amount can be accurately grasped. As described above, the number of packers to be installed may be appropriately changed according to test conditions and the like.

[Effect of the Invention] As described above, the present invention provides three or more pneumatic pressure cut-off packers, pressure sensors provided in a plurality of packer sections formed by the pneumatic pressure cut-off packers, and an opening in any one packer section. Since the permeability test apparatus is provided with a water channel, the distribution of permeability along the bore hole can be finely and continuously and easily obtained by using a single bore hole. In the present invention, since the analysis of the measurement data is performed numerically by constructing a permeability distribution model, the presence or absence and position of the impermeable boundary, whether or not the stratum is homogeneous between the transmission point and the reception point, etc. This is not a problem, and therefore, it can be applied to the investigation of the permeability and the stratum structure of various types of ground in the general civil engineering field.

Further, since it is only necessary to accurately record the change over time in the flow rate as a boundary condition required for analysis, the mechanism of the variable water pressure generation / supply device can be simplified and downsized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a test apparatus according to the present invention, FIG. 2 is a conceptual diagram of a water permeability test using the test apparatus, FIG. 3 is an explanatory view of a water permeability distribution model used for analysis, FIG. Is an explanatory diagram showing an example of a test result, and FIG. 5 is a flowchart showing an example of a test method. 10 Packer part, 12 Center pipe, 14 Flexible packer tube, 16 Connecting pipe, 18 Perforated water pipe, 20 Pressure sensor, 22 Air tube for packer expansion.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Kazumasa Ito 4-6-6 Kudankita, Chiyoda-ku, Tokyo Applied Geology Co., Ltd. (56) References JP-A-3-55310 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) E02D 1/00 E21B 33/12 G01L 27/00

Claims (5)

(57) [Claims] 1. A pneumatic pressure cut-off packer section which is arranged in a row at intervals, pressure sensors provided in a plurality of packer sections formed by adjacent packer sections, respectively, A single-hole variable hydraulic pressure permeation test apparatus having a water injection passage which is open only in any one of the packer sections. 2. Three or more pneumatic pressure shut-off packers disposed in a row in a borehole and spaced apart from each other;
A pressure sensor provided in each of a plurality of packer sections formed by adjacent packer sections; a water injection path having water permeability in the apparatus axial direction and opening only in any one packer section; and a water injection path installed on the ground. A single-hole variable hydraulic pressure permeation test apparatus, comprising: a variable hydraulic pressure generation / supply device connected to the apparatus; and a device for recording and analyzing signals from each pressure sensor. 3. After the packer section is inflated by using the apparatus according to claim 2, the change over time in the flow rate can be grasped from the variable water pressure generating / supplying device to the transmission packer section where it is opened through the water injection passage. A single-hole fluctuating water pressure characterized by adding a fluctuating water pressure, measuring the response pressure in the other receiving packer sections to that, and obtaining the horizontal and vertical permeability distributions between the transmitting packer section and the receiving packer section. Water permeability test method. 4. A region to be analyzed around a boring hole is divided into a number of axially symmetrical ring elements, and a cylindrical coordinate system model is constructed in which each ring element has permeability as a parameter. Calculates the response pressure in the receiving packer section by numerical analysis based on the mass balance equation with the inflow and outflow of the three-dimensional axisymmetric gas-liquid two-phase permeate flow as the boundary conditions, compares the calculated value with the measured value, and calculates the error. 4. The method according to claim 3, wherein the water permeability distribution model is modified by evaluating and changing parameters indicating permeability, and the above-mentioned numerical analysis-model modification operation is repeated to obtain an optimal model. 5. The operation of obtaining the horizontal and vertical permeability distributions of the ground between the transmission packer section and the reception packer section is performed by changing the depth in the borehole of the test device,
5. The method according to claim 4, wherein the distribution of the hydraulic conductivity of the ground over the entire length of the borehole is determined.