JP2000073684A - In-situ water-sampling method in thick sedimentary-rock stratum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-situ water-sampling method, by which water can be sampled under an in-situ state by conducting fresh-water excavation applying directional drilling technique to an aquifer in a thick muddy sedimentary rock and chemical analysis can be executed with accuracy by the water sampling. SOLUTION: A main-tunnel well 2 is excavated by a rotary type excavation method using swelling inhibition type slurry as an excavation fluid, a whipstock 8 is installed in KOP depth for executing side stacking for sampling stratum water under an in-situ, a window hole 9 is bored, directional drilling is conducted up to a section just above an aimed stratum by a downhaul motor and MWD organization through the window hole 9, and a casing 15 is set to the directional drilling section. The outside of the casing 15 is filled with cement and water-shielded, the excavation fluid is replaced with fresh water, a water- sampling well 16 is directional-drilled by drill strings, tubing strings 18, to which a bare-hole packer 19 is set, is inserted into the water-sampling well 16, the main-tunnel well 2 and the water-sampling well 16 are interrupted by the bare- hole packer, and water sampling and measurement are conducted under the in-situ state of an aquifer 7 through the insides of the tubing strings 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of excavating a main well and a sampling well by using a rotary excavation method, and in particular, an in-situ water sampling method in an aquifer interposed between thick sedimentary rock layers. It is about.

[0002]

2. Description of the Related Art The Power Reactor Nuclear Fuel Development Corporation is conducting research to confirm the safety of the underground disposal of high-level radioactive waste. High-level radioactive waste buried underground will leak to a point where its radioactivity does not leak to the ground or affect humans until its radioactivity intensity is at the same level as natural uranium deposits. Not required. It is considered that the radioactive leakage is due to the fact that the waste itself comes to the ground due to crustal deformation and the movement of groundwater.

[0003] In order to prove that there is no leakage of radioactivity due to this movement of groundwater, a deep well is drilled and groundwater in the formation is sampled and investigated.
The groundwater to be investigated includes not only so-called groundwater, which is moving in large quantities, but also trace amounts of groundwater contained in strata and rocks. Investigations of this trace amount of groundwater are not only physical investigations such as the amount of groundwater sampled, but also investigations mainly on chemical analysis. For this reason, it is required that the drilling of the survey well should be performed in fresh water without using muddy water which affects the chemical analysis.

In order to collect formation water in situ, it is basically to use clear water as a drilling fluid. However, it is impossible to excavate a thick muddy sedimentary rock layer over a long distance with clear water. . This is because swelling and collapse of the clay mineral contained in the muddy sedimentary rock layer causes excavation obstacles.
In order to minimize this excavation hindrance, it is preferable to use muddy water of a swelling suppression type or the like.

In this well, in order to prevent collapse of the well wall, the casing is set immediately after excavation, and the gap between the outside of the casing and the hole wall is filled with cement, thereby directly or indirectly in the vertical direction. It is necessary to prevent the adjacent layers from communicating with each other through the gap, and in particular, to impregnate the aquifer with full-hole cementing.

[0006] When drilling is performed using muddy water, mud filtration (filtration water) from the mud wall generated during the open pit time (drilling time) permeates into the aquifer. Therefore, in order to collect water at the original position, it is necessary to collect water at a position below the mud filtration rate.

The amount of dewatered mud filtrate that permeates into the aquifer from the circulating mud is calculated by the following equation (new mud for boring: Bunno Okino, Gihodo Shuppan, pp. 64-66). Q = {[2K (Cs / Ms-1) PT] / μ} ^0.5 A (1) where, Q = dehydration amount, K = permeability, Cs = solid concentration in mud wall, Ms = mud in muddy water Solid concentration, P = differential pressure, T
= Time, μ = viscosity of liquid phase, A = filtration area, range (distance) through which mudfiltrate permeates, the differential pressure between mud column pressure and formation pressure during excavation is reduced, and The shorter the time, the smaller the time.

[0008]

As described above, when the conventional rotary excavation method is used for excavation of the investigation well, the following problem occurs. In order to excavate a thick muddy sedimentary rock layer, it is preferable to use muddy water such as a swelling suppression type, and it is difficult to excavate a long distance in fresh water. By using muddy water, penetration of mudfiltrate into the aquifer cannot be avoided. It is necessary to install casing pipes to prevent collapse of the pit wall. In order to prevent communication between the aquifer layers at different levels in the vertical direction, it is necessary to fill the gap between the casing and the hole wall with cement to completely cement the full hole. Due to the cementing, the aquifer near the well is contaminated with cement.

The present inventor has proposed a depth of about 1000 to 3000 m.
As a result of various studies on the in-situ water sampling method from the aquifer sandwiched between thick muddy sedimentary rock layers, taking into account the technical problems inevitable for well drilling, We developed a drilling method for excavating water in Shimizu, and found a method that enables in situ water sampling in a deep aquifer by this drilling method.

An object of the present invention is to provide an in-situ water sampling method in an aquifer sandwiched between thick muddy sedimentary rock layers proposed based on the above findings.

[0011]

In order to achieve the above-mentioned object, the present invention provides a method for drilling a main well by a rotary drilling method using muddy water as a drilling fluid. When drilling a branch well from the main well to the outside of the permeation area of the mud filtrate calculated using the above method, a KOP (Kick) for performing the branch excavation in order to collect in situ formation water is used. Off Point) A whip stock is installed in the main well at a depth, and then a window hole for branch digging is drilled in a casing of the well using the whip stock as a guide, and a down hole is formed through the window hole. Using a motor and MWD knitting, slant excavation is performed using mud water as the drilling fluid to immediately above the target layer, and a casing is set in the inclined hole where the slant was excavated, and cement is filled outside the casing to block water. Next, the drilling fluid is replaced with fresh water, and a sampling well is inclinedly excavated to a target position so as to extend from the inclined hole, and a tubing string set with an open hole packer is inserted into this well, and the main well is inserted with the open hole packer. The branch well and the sampling well communicating with the well are shut off, and sampling and measurement of the aquifer in situ are performed through the tubing strings.

In the present invention, a main well is excavated by a rotary excavation method using swelling suppression type mud as a drilling fluid, and a mud filtrate calculated using data measured during the excavation of the main well penetrates. When excavating a branch well from the main well to the outside of the range, a KOP (KickOf) for performing the branch excavation in order to collect formation water in an in-situ state.
f Point) installing a whip stock in the main well at a depth, and then drilling a window hole for digging using high viscosity muddy water as a drilling fluid in a casing of the well using the whip stock as a guide; Using the downhole motor and MWD knitting, the swelling-suppressing type mud is used as a drilling fluid, and the slope is excavated through the window hole to just above the target layer. The casing is set with a liner hanger and the outside of the casing is filled with cement to block water. Then, the drilling fluid was replaced with fresh water, the sampling well was slopingly drilled to a target position so as to extend from the sloped hole, tubing strings set with a borehole packer were inserted into the sampling well, and the main well was inserted with the borehole packer. Isolate the branch wells and sampling wells communicating with the wells, and perform sampling and measurement of the aquifer in situ through the tubing strings. Features.

In the present invention, the excavation angle of the water sampling well is characterized by being inclined downward at an acute angle with respect to the main well.

In the present invention, the underground water of the sampling well is
It is advisable to cut to a fluid pressure slightly lower than the aquifer formation pressure measured at the time of drilling.

In the present invention, the excavation position of the water sampling well is at least three times the penetration distance of the mud filtration.

According to the present invention, first, a well is used for drilling a thick muddy sedimentary rock layer by a rotary drilling method using muddy water of a swelling suppression type or the like as a drilling fluid, and confirming the existence of a water sampling target layer. Excavation, set the casing to prevent collapse of the hole wall, and completely block the aquifer with full hole cementing.

The permeation range (distance) of the mud filtration rate is calculated from the measured electric logging data and mud data of the water sampling target layer detected during the excavation of the well. Observing the error and the safety factor of the various data used in the calculation, the deviation is calculated using the calculated mud filtration rate permeation distance three times as a guide, and the inclination angle that does not hinder the lowering of the tubing strings and the water sampling work. Calculate the KOP (KickOff Point) depth to carry out the sampling well digging,
A whip stock is installed at the determined KOP point, and a window hole is drilled in the casing of the well. At this time, high-viscosity muddy water may be used in order not to leave gold shavings in the pit.

Through the window hole, using a swelling-suppressing type mud as a drilling fluid, a downhole motor, MWD knitting, and a branch well are slopingly drilled to just above a target layer, a casing is set with a liner hanger, and the casing is placed outside the casing. Filling with cement to block the water, replacing the drilling fluid with fresh water, and sloping the sampling well to the target position using ordinary drill strings.
The drilling fluid used at this time is clear water so as not to disturb the original state of the aquifer. When the drilling of the sampling well is completed, the underground water is trimmed until the pressure becomes lower than the formation pressure measured at the time of drilling of the well, and the inside of the sampling well tends to overflow.

A tubing string with a perforated tube set at the tip and an open hole packer in the middle is lowered,
Once the packer is activated and the well and main well are shut off, water is collected in situ from the aquifer through the tubing strings.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main well 2 in which a thick muddy sedimentary rock layer 1 has been excavated to a depth of about 3000 m by a rotary excavation method using swelling suppression type muddy water as an excavating fluid. Inside the main well 2, there are 20 wells for preventing collapse of the well wall.
Inch casing 3, 13,3 / 8 inch casing 4, 9.5 / 8 inch casing 5, descend and set in order, complete cementing between the casings 3,4,5 and the pit wall. With this cement layer 6, each of the aquifer layers 7, 7 is completely shut off. Further, detection of the target aquifers 7, 7 from the various electrical logging data and mud data performed before the casings 3, 4, 5 were lowered, the formation pressure of the aquifers 7, 7, the permeability, Obtain data such as effective layer thickness and use it as basic data for calculating the penetration range (distance) of mud filtration. During the excavation of the well 2, the dewatering amount of the mudfiltrate that penetrates into the aquifers 7 from the circulating mud is calculated using the equation shown in the above-mentioned [0007].

The deviation is determined by using a value three times as large as the calculated penetration depth of the mud filtrate, and the below-described water sampling well is dug at a tilt angle that does not hinder the water sampling operation. Calculate KOP (Kick Off Point).

Next, as shown in FIG. 2, the whip stock 8 is set at the determined KOP point. Next, as shown in FIG. 3, a branch well in a state in which the casing 5 in the well 2 is inclined downward as described below on the casing 5 using the inclined surface 8 a of the installed whip stock 8 as a guide. A window hole 9 for digging a water sampling well connected in series with the milling hole is drilled by a milling string 10 having a steel pipe cutter 11 set at the tip. It is preferable to use a highly viscous muddy water as a drilling fluid in order to remove gold dust generated when the window hole 9 is drilled.

Next, as shown in FIG. 3, the milling is continued until the milling strings 10 reach the formation 1, and when the drilling of the window hole 9 is completed, the drilling fluid, that is, the high-viscosity fluid passes through the milling strings 10. The muddy water is drained to the outside, replaced with swelling-inhibited muddy water, and the milling strings 10 are raised and extracted from the well 2.

After the milling strings 10 have been extracted, as shown in FIG.
through the perforated window 9 through the drilling tool 13 with
With the downhole motor and the MWD knitting, the thick muddy sedimentary rock layer 1 is dug into the inclined hole 21 right above the target position while appropriately increasing the inclination angle of the excavation cutter portion 12 in the downhole motor in the downhole motor. In other words, the water sampling layer 7 to be sampled by branch excavation is digged up to just above the water sampling layer 7 at a distance where the penetration of the mud filtration does not reach. Next, as shown in FIG.
The runner hanger 14 is locked to the inner casing 5,
The runner hanger 14 is used to set a flexible casing 15 in the inclined hole 21.
Between the lower and outer peripheral surfaces of the hole and the hole wall with cement 6. Next, the drilling fluid is replaced with fresh water, and the water sampling well 16 is tilted and drilled downward with a drill string (not shown) having a normal formation to a target position.

Next, an electric logging is carried out to confirm that the target aquifer has been excavated and to measure the properties of the aquifer 7. The underground water is trimmed until the fluid pressure becomes slightly lower than the formation pressure of the aquifer 7 measured during the excavation of the main well 2, and the inside of the branch well is made to overflow. Next, as shown in FIG. 6, a tubing string 18 in which a perforated tube 17 having a large number of through holes 17a is set at the tip is inserted.
At this time, since the water retention layer 7 tends to overflow as described above, the influence of the insertion of the tubing strings 18 does not affect the water retention layer 7.

The open hole packer 19 set near the aperture tube 17 of the tubing strings 18 is operated so as to expand, and in a state where the sampling well and the aquifer 7 are in communication, the aquifer 7 and the branch Well and main well 2 communicating with it
Cut off between. The open hole packer 19 may be either a mechanical type or a hydraulic type. When the hydraulic type is used, it is operated by supplying a fluid through an air supply pipe 20 shown in FIG.

By blocking the aquifer 7 from the branch well and the main well 2 communicating therewith, the aquifer 7 recovers its original position. In-situ formation water sampling
Testing becomes possible.

In practicing the present invention, when drilling a sampling well, the type of rig to be used, the drilling depth, the drilling diameter, the casing diameter, the casing program, the type of drill strings, the drilling fluid replacement time, the branch well Are variously possible combinations, and are not limited to the above-mentioned specific combination, and an excavation method used in an appropriate combination can also be adopted.

In practicing the present invention, a conventionally known downhole motor can be used. Usually, the downhole motor is connected next to the bit at the tip of the drill string, and the downhole motor is driven by the flow of circulating muddy water. It is a driven excavator. In practicing the present invention, conventionally known MWDs can be used.
This device is connected next to the downhole motor at the tip of the drill string, measures the azimuth and inclination during excavation as needed, and directs the bit downhole motor freely in the desired direction.

[0030]

As described above, according to the present invention, a main well is drilled by a rotary drilling method using muddy water of a swelling suppression type or the like as a drilling fluid, and data measured at the time of drilling the main well is obtained. When drilling a branch well from the main well to outside the permeation range of the mud filtrate calculated using,
A whip stock is installed in the main well at a KOP (Kick Off Point) depth for performing the branch excavation in order to collect the in situ formation water, and then the whip stock is used as a guide for the main well. Using a mud such as a high-viscosity mud as a drilling fluid, a window hole for branch excavation is drilled in a casing of the vehicle, and a downhole motor, MWD
In knitting, swelling suppression type mud is used as a drilling fluid to diagonally excavate immediately above the target layer, the casing is set with a liner hanger, and the outside of the casing is filled with cement to block out water, and the drilling fluid is replaced with fresh water. A sampling well is slopingly excavated to a target position so as to extend from the hole, tubing strings set with an open hole packer are inserted into the well, and a branch well and a sampling well communicating with the main well at the open hole packer. And the aquifer is sampled and measured in situ through the tubing strings.Thus, the vicinity of the well in the aquifer is not contaminated with cement or muddy water. In situ water sampling from the aquifer sandwiched between the sedimentary rock layers is possible, enabling accurate surveys. Therefore, the in-situ water sampling method for the thick sedimentary rock layer of the present invention greatly contributes to the geological investigation for the underground disposal (deep underground disposal) of high-level radioactive waste, which is increasingly required.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional side view showing a state in which a well is excavated by a rotary excavation method using muddy water, a casing is set, and cementing is performed between the casing and a stratum.

FIG. 2 is a partially cutaway longitudinal sectional view showing a situation where whip stock is set at a determined KOP point in the well in order to carry out the in-situ water sampling method according to the present invention.

FIG. 3 is a longitudinal sectional view showing a situation in which a window hole is drilled in a casing of the well to branch out a water sampling well.

FIG. 4 is a partially cut-away longitudinal sectional view showing a situation where a sampling well is excavated through a window hole of a casing.

FIG. 5 is a partially cutaway longitudinal sectional view showing a situation in which a casing for preventing collapse of a water sampling well drilled through a window hole is set.

FIG. 6: Inserting tubing strings into a sampling well,
FIG. 3 is a partially cut-away longitudinal sectional view showing a state in which a main well and a water sampling well (aquifer) are cut off by an open hole packer set in the tubing strings.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Thick sedimentary rock layer 2 Wells 3,4,5,15 Casing 6 Cement layer 7 Reservoir layer 8 Whip stock 9 Window hole 10 Milling string 11 Cutter for steel pipe 12 Bit for formation 13 Drill string (downhole motor, M
WD) 14 Liner hanger 16 Sampling well 17 Drilling tube 18 Tubing strings 19 Open hole packer 20 Air supply tube 21 Inclined hole

Claims (5)

[Claims] A well is drilled by a rotary drilling method using muddy water as a drilling fluid, and the hole is drilled out of a range where a mud filtration rate calculated using data measured at the time of drilling the well is penetrated. When excavating a branch well from a well, whip stock is installed in the main well at a KOP (Kick Off Point) depth for carrying out the branch excavation in order to collect formation water in situ, Then, using the whip stock as a guide, a window hole for digging is drilled in the casing of the well, and through the window hole, mud water is used as a drilling fluid by a downhole motor and MWD knitting to just above a target layer. Drilling is performed, and the casing is set in the portion of the sloped hole that has been sloped and filled with cement outside the casing to block water.Then, the drilling fluid is replaced with fresh water and extended from the sloped hole. Diagonally excavating the sampling well to the target position as described above, tubing strings set with a bare hole packer are inserted into this sampling well, and the branch well and the sampling well communicating with the well are cut off with the above-mentioned borehole packer, An in-situ water sampling method for a thick sedimentary rock layer, wherein water is collected and measured in an in-situ state of an aquifer through the tubing strings. 2. The well is drilled by a rotary drilling method using swelling-suppressing type mud as a drilling fluid, and the mud filtration rate calculated using data measured during the drilling of the well is out of a permeation range. When drilling a branch well from the main well, whip stock is installed in the main well at a KOP (KickOff Point) depth for carrying out the branch digging in order to collect in situ formation water. Then, using the whip stock as a guide, a window for drilling is drilled in the casing of the well using high-viscosity muddy water as a drilling fluid, and a downhole motor, M
In WD knitting, swelling-suppressing type mud is used as a drilling fluid to diagonally excavate immediately above the target layer, the casing is set with a liner hanger, and the outside of the casing is filled with cement to block out water, and the drilling fluid is replaced with fresh water. A water sampling well is inclinedly excavated to a target position so as to extend from the inclined hole, a tubing string set with an open hole packer is inserted into the water well, and a branch well communicating with the main well through the open hole packer is sampled. An in-situ water sampling method for a thick sedimentary rock layer, wherein a water well is cut off and water is collected and measured in the in-situ state of the aquifer through the tubing strings. 3. The thick sedimentary rock layer according to claim 1, wherein the excavation angle of the water sampling well is inclined downward at an acute angle with respect to the main well. Positional sampling. 4. The in-situ sampling of a thick sedimentary rock layer according to claim 1, wherein the underground water of the sampling well is cut to a fluid pressure slightly lower than the aquifer formation pressure measured during drilling of the well. Water law. 5. The in-situ water sampling method for a thick sedimentary rock layer according to claim 1, wherein an excavation position of the water sampling well is at least three times a permeation distance of a mud filtrate.