阅读说明：本技术 一种占位钻具法单筒三井表层钻井方法 (Single-cylinder three-well surface drilling method by using space-occupying drilling tool method ) 是由 刘书杰 黄熠 管申 郭浩 赵宝祥 何连 刘贤玉 杨可三 刘立焱 朱志潜 王养锋 于 2020-12-03 设计创作，主要内容包括：本发明一种占位钻具法单筒三井表层钻井方法,包括以下步骤：S1.在隔水套管的上方安装36英寸的单筒三井基盘；S2.依次移井架至B井和C井,并在B井和C井中各自下入占位钻具；S3.移井架至A井,对A井进行开井固井作业；S4.用鱼线吊测法确认A井水泥面高度；S5.移井架至B井,对B井进行开井固井作业；S6.用鱼线吊测法确认B井水泥面高度；S7.移井架至C井,对C井进行开井固井作业。本发明配合独特设计的占位钻具中具有的14.25英寸的分隔串的有效占位作用,实现单筒三井的钻井方法,1个井筒3个井眼独立闭路作业,互不干扰,增加单位面积布井密度,充分提高槽口利用率,从而缓解海上油田开采槽口紧缺的压力,并大幅降低开采成本。(The invention relates to a single-cylinder triple-well surface drilling method by using an occupying drilling tool method, which comprises the following steps of: s1, mounting a 36-inch single-barrel three-well base plate above a water-resisting casing; s2, sequentially moving the derrick to a well B and a well C, and respectively putting an occupying drilling tool into the well B and the well C; s3, moving the derrick to the well A, and performing well opening and cementing operation on the well A; s4, confirming the cement surface height of the well A by using a fishing line hanging measurement method; s5, moving the derrick to a well B, and performing well opening and cementing operation on the well B; s6, confirming the cement surface height of the well B by using a fishing line hanging measurement method; and S7, moving the derrick to the well C, and performing well opening and cementing operation on the well C. The invention is matched with the effective occupation effect of the 14.25-inch separation string in the uniquely designed occupation drilling tool to realize the drilling method of the single-cylinder three-well, 1 shaft and 3 well bores are independently operated in a closed circuit without mutual interference, the well distribution density in unit area is increased, and the notch utilization rate is fully improved, thereby relieving the pressure of the shortage of the exploitation notches of the offshore oil field and greatly reducing the exploitation cost.)

1. A single-cylinder triple-well surface drilling method by using an occupying drilling tool method is characterized by comprising the following steps:

s1, a 36-inch riser (12) is installed on a pre-production well, a 36-inch single-barrel three-well base plate (1) is installed above the riser (12), and an A well (2), a B well (3) and a C well (4) are correspondingly arranged below the single-barrel three-well base plate (1);

s2, sequentially moving the derrick to a well B (3) and a well C (4), respectively lowering an occupying drilling tool (11) into the well B (3) and the well C (4), wherein the occupying drilling tool (11) is connected to a hanger (6) arranged at a corresponding well mouth, and the occupying drilling tool (11) comprises a 14.25-inch plug (10) and a plurality of groups of separated connecting structures which are sequentially connected from bottom to top; the separation connecting structure comprises a 14.25-inch separation string (9) and 5-inch drill pipes (8) connected to two ends of the separation string (9), and the joint overlapping height between every two adjacent separation strings (9) of the well B (3) and the well C (4) is more than 20 cm;

s3, moving the derrick to the well A (2), and performing well opening and cementing operation on the well A (2);

s4, after the well A (2) completes well opening and cementing operation, cement paste waits for more than 24 hours, the derrick is moved to the well B (3) during the cement paste waiting for setting, an occupying drilling tool (11) in the well B (3) is lifted out, and the height of the cement surface of the well A (2) is confirmed by a fish line hanging measurement method through a cement observation hole (5) formed in the single-tube three-well base plate (1);

s5, moving the derrick to the well B (3), and performing well opening and cementing operation on the well B (3);

s6, after the well B (3) completes well opening and cementing operation, cement paste waits for more than 24 hours, the derrick is moved to the well C (4) during the cement paste waiting for setting, the occupying drilling tool (11) is lifted out, and the height of the cement surface of the well B (3) is confirmed by a fish line hanging measurement method through a cement observation hole (5) formed in the single-tube three-well base plate (1);

and S7, moving the derrick to the C well (4), and performing well opening and cementing operation on the C well (4).

2. The surface drilling method of monotube triple well according to claim 1, characterized in that the well-opening cementing operation comprises the following steps:

s31, sequentially installing a lifting pipe, a blowout preventer stack and a horn pipe from bottom to top on a wellhead of a corresponding well, and carrying out pressure test on the blowout preventer;

s32, well first-opening operation: drilling to a set well depth by adopting a well section drilling tool assembly (19) in a corresponding well, circularly flushing the waterproof casing (12) through a circulating channel arranged in the occupation drilling tool (11), and taking out the well section drilling tool assembly (19);

s33, putting a 11.75-inch surface casing (14) in place in the corresponding well, connecting the surface casing (14) to the hanger (6) of the corresponding well mouth in a sealing manner, and then performing well cementation operation;

and S34, after the surface casing (14) is connected with the hanger (6), cutting and recovering the redundant part of the surface casing (14) outside the wellhead, and circularly flushing the cement (16) in the waterproof casing (12) by using drilling fluid through a circulating channel arranged in the space occupying drilling tool (11) during the well cementation operation and within a plurality of hours after the well cementation operation is finished.

3. The single-barrel triple-surface hole drilling method by using the space occupying drilling tool (11) according to claim 2, wherein the space occupying drilling tool (11) is provided with a 2-inch drift diameter capable of forming the circulating channel inside the choke plug (10) and the separation string (9).

4. The method of claim 1, wherein the lowering position of the plug (10) in the space occupying drilling tool (11) is inside the riser (12) and the bottom surface of the plug is spaced from the bottom surface of the riser (12) by less than 2 meters.

5. The space occupying drilling tool (11) method triple barrel surface drilling method according to claim 1, wherein in the space occupying drilling tool (11), the spacing between the separation strings (9) in two adjacent separation connection structures is less than 20 meters.

6. The space occupying drill (11) method triple barrel surface drilling method according to claim 1, wherein the length of the largest part of the outer diameter on the spacer string (9) is 30-35 cm.

7. The surface drilling method of monotube triple well by space occupying drill (11) according to claim 2, wherein the surface casing (14) is a ferrule-less casing or a ferrule-joint casing with a bevel on top of the ferrule.

8. The space occupying drilling tool (11) method triple barrel surface drilling method according to claim 2, wherein the interval drilling tool assembly (19) is: the 14-inch roller bit (13) + a motor + MWD + a non-magnetic drill collar + a centralizer + a jar + a heavy drill rod + a drill rod.

9. The space-occupying drilling tool (11) -method triple-barrel surface drilling method according to claim 2, wherein in step S4, the derrick is moved to the B-well (3) and the C-well (4) during the waiting period of cement paste, and the space-occupying drilling tool (11) in the B-well (3) and the C-well (4) is lifted out and lowered into the space-occupying drilling tool (11) in the C-well (4) again.

10. The surface drilling method of single-barrel triple-well by space occupying drilling tool (11) according to claim 1, characterized in that the fish line hang measurement method is: use the fish tape to connect the plummet, transfer through cement observation hole (5) the plummet is to meeting and is hindered, measures the fish tape length of putting in, according to the fish tape length of putting in calculates cement stopper face degree of depth, and its computational formula is: the depth of the cement plug surface is equal to the length of the thrown fishing line plus the distance from the single-cylinder three-well base plate (1) to the surface of the rotating disc.

Technical Field

The invention relates to the field of offshore oil drilling engineering, in particular to a single-cylinder triple-well surface drilling method by using an occupying drilling tool method.

Background

On an offshore production platform of offshore oil, after years of development, a large number of oil fields (groups) enter the middle and later stages of production construction, severe problems of non-notch availability, notch unavailability, notch inexhaustibility and the like are faced to newly-discovered oil fields and marginal oil field exploitation, and the offshore oil field exploitation faces the pressure of notch shortage, so that precious notch resources are efficiently utilized, and the offshore production platform becomes an important measure for oil field production conservation; for example, Chinese patent CN110145275A discloses a surface layer drilling and completion process of single-barrel double wells by using an occupying drilling tool method, which can realize shallow deviation of well tracks and realize non-interference of well tracks of single-barrel double wells, so as to achieve the purpose of drilling two wells from a single notch and solve the problem that a reservoir cannot be fully developed due to insufficient platform notches; however, as the number of the notches is less and less, the single-cylinder double wells can not meet the requirements slowly, the utilization rate of the notches is not high enough, the pressure of the offshore oilfield exploitation notches in shortage can not be relieved to a greater extent, and the exploitation cost is higher.

Disclosure of Invention

The invention provides a single-cylinder three-well surface drilling method by using an occupying drilling tool method, aiming at solving the problems that a single-cylinder two-well can not meet the requirements slowly and the utilization rate of a notch is not high enough along with the fact that the notches are fewer and fewer in the background technology. The invention realizes single-cylinder triple well, efficiently utilizes the notch, thereby relieving the pressure of the shortage of the offshore oilfield exploitation notch and greatly reducing the exploitation cost.

In order to solve the technical problems, the invention adopts the technical scheme that: a single-cylinder triple-well surface drilling method by using an occupying drilling tool method comprises the following steps:

s1, installing a 36-inch riser on a pre-production well, installing a 36-inch single-barrel three-well base plate above the riser, and correspondingly and respectively arranging a well A, a well B and a well C below the single-barrel three-well base plate;

s2, sequentially moving the derrick to a well B and a well C, and respectively putting an occupying drilling tool in the well B and the well C, wherein the occupying drilling tool comprises a 14.25-inch plug and a plurality of groups of separated connecting structures which are sequentially connected from bottom to top; each group of separation connecting structures comprises a 14.25-inch separation string and 5-inch drill pipes connected to two ends of the separation string, the top 5-inch drill pipe of the separation connecting structure at the topmost end is connected to a hanger arranged at a corresponding well mouth, and the joint overlapping height between every two adjacent separation strings of the well B and the well C is more than 20 cm;

s3, moving the derrick to the well A, and performing well opening and cementing operation on the well A;

s4, after the well A finishes the well opening and cementing operation, cement paste waits for more than 24 hours, the derrick is moved to the well B during the cement paste waiting for setting, an occupying drilling tool in the well B is lifted out, and the cement surface height of the well A is confirmed by a fish wire hanging measurement method through a cement observation hole arranged on the single-tube three-well base plate;

s5, moving the derrick to a well B, and performing well opening and cementing operation on the well B;

s6, after the well B finishes the well opening and cementing operation, waiting for more than 24 hours by cement paste, moving the derrick to the well C during waiting for setting by the cement paste, taking out the occupying drilling tool, and confirming the cement surface height of the well B by a fishing line hanging measurement method through a cement observation hole arranged on the single-tube three-well base plate;

and S7, moving the derrick to the well C, and performing well opening and cementing operation on the well C.

Further, the well opening and cementing operation comprises the following steps:

s31, sequentially installing a lifting pipe, a blowout preventer stack and a horn pipe from bottom to top on a wellhead of a corresponding well, and carrying out pressure test on the blowout preventer;

s32, well first-opening operation: drilling to a set well depth by adopting a well section drilling tool assembly in a corresponding well, circularly flushing the waterproof casing through a circulating channel arranged in the occupation drilling tool, and taking out the well section drilling tool assembly;

s33, putting 11.75-inch surface casing pipes into the corresponding wells in place, connecting the surface casing pipes to the hangers at the well mouths of the corresponding wells in a sealing manner, and then performing well cementation operation;

and S34, after the surface casing pipe is connected with the hanger, cutting and recovering the redundant part of the surface casing pipe outside the wellhead, and circularly flushing the cement in the water separating sleeve by using drilling fluid through a circulating channel arranged in the space occupying drilling tool during the well cementation operation and within a plurality of hours after the well cementation operation is finished.

Furthermore, in the space occupying drilling tool, the inner parts of the plug and the separation string are respectively provided with a 2-inch drift diameter capable of forming the circulation channel.

Further, the plug descending position in the occupying drilling tool is positioned inside the riser, and the distance between the plug descending position and the bottom of the riser is less than 2 m; the lower position of the water-proof casing pipe is lower than the lower position of the plug, so that the plug cannot extend out of the water-proof guide pipe, otherwise, the position occupied by the plug cannot be occupied, and meanwhile, if the plug is out of the water-proof guide pipe, the leakage of the water-proof guide pipe out of the stratum is easily caused, so that the leakage of the water-proof guide pipe out of the stratum is caused; if the spacing is too large, it will not be a significant footprint, so that the spacing is typically less than 2 meters.

Further, in the space occupying drilling tool, the distance between the separation strings in two adjacent separation connecting structures is less than 20 meters.

Further, the length of the largest part of the outer diameter of the separation string is 30-35 cm.

Preferably, the surface casing is a non-joint casing or a joint casing with a guide angle arranged on the upper and lower sides of the joint.

Further, the well section drilling tool assembly is: 14-inch roller bit + motor + MWD + non-magnetic drill collar + centralizer + jar + heavy drill rod + drill rod.

Preferably, in step S4, the derrick is moved to the B well and the C well during the cement grout waiting period, and the space occupying drilling tools in the B well and the C well are respectively lifted out and then lowered into the space occupying drilling tools in the C well again. When the occupying drilling tool in the step B is pulled out, the occupying drilling tool in the step C is pulled out, and then the occupying drilling tool is put in again, so that the occupying drilling tool can be prevented from twisting.

Further, the fishing line hanging measuring method comprises the following steps: use the fish tape to connect the lead weight, transfer through cement observation hole the lead weight is to meeting and hindering, measures the fish tape length of putting in, according to the fish tape length of putting in calculates cement stopper face degree of depth, and its computational formula is: the depth of the cement plug surface is equal to the length of the thrown fishing line plus the distance from the single-cylinder three-well base plate to the surface of the rotating disc.

Compared with the prior art, the beneficial effects are:

1. in a 36-inch water-resisting casing pipe with smaller size and stronger strength, the drilling method of the single-barrel three-well is realized by skillful structural design and method steps and by matching with the effective occupation effect of the 14.25-inch separation string in the uniquely-designed occupation drilling tool, 3 well bores of 1 shaft are independently operated in a closed circuit mode without mutual interference, the well distribution density in unit area is increased, the utilization rate of notches is fully improved, the pressure of shortage of exploitation notches of an offshore oil field is relieved, and the exploitation cost is greatly reduced.

2. By using the non-joint hoop surface casing, the three-hole underground surface casing entering operation can be completed more safely and efficiently; and the occupied drilling tool is flushed during and after well cementation, and the occupied drilling tool is taken out, so that the occupied drilling tool is prevented from twisting, and the safety of a shaft can be further ensured.

Drawings

FIG. 1 is a schematic view of the construction of a single barrel triple well slot of the present invention.

FIG. 2 is a schematic illustration of the drilling of a well A in accordance with the present invention.

FIG. 3 is a schematic illustration of the present invention for drilling a B-well.

Fig. 4 is a schematic illustration of the invention for drilling a C well.

Figure 5 is a schematic representation of the completion of a surface drilling operation of the present invention.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.

The embodiment provides a single-cylinder triple-well surface drilling method by using an occupying drilling tool method, which comprises the following steps of:

s1, installing a 36-inch marine riser 12 on a pre-production well, installing a 36-inch single-barrel three-well base plate 1 above the marine riser 12, and correspondingly and respectively arranging a well A2, a well B3 and a well C4 below the single-barrel three-well base plate 1; after the single-cylinder three-well base plate 1 is installed, the notch of the single-cylinder three-well is shown in figure 1;

s2, as shown in figure 2, sequentially moving the derrick to a well B3 and a well C4, respectively lowering an occupying drilling tool 11 into the well B3 and the well C4, wherein the occupying drilling tool 11 comprises a 14.25-inch plug 10 and a plurality of component partition connecting structures which are sequentially connected from bottom to top; each group of separation connecting structures comprises 14.25-inch separation strings 9 and 5-inch drill pipes 8 connected to two ends of each separation string 9, the topmost separation connecting structure is connected to a hanger 6 arranged at a corresponding wellhead through the 5-inch drill pipe 8 at the top of the topmost separation connecting structure, and the joint overlapping height between every two adjacent separation strings 9 of the well B3 and the well C4 is more than 20 cm; the height of the part with the outer diameter of 14.25 inches on the separation strings 9 is 30cm, the structural distribution on the space occupying drilling tools of the B well and the C well is basically the same, so that each adjacent separation string has a certain overlapping part in height, the separation strings are in one-to-one correspondence in order to effectively occupy space, and the attaching overlapping height between each two adjacent separation strings 9 of the B well 3 and the C well 4 is at least more than 20 cm;

s3, moving the derrick to the well A2, and performing well opening and cementing operation on the well A2;

s4, as shown in figure 3, after the well A2 finishes the well opening and cementing operation, cement paste waits for more than 24 hours to be solidified, the derrick is moved to the well B3 and the well C4 in the cement paste waiting period, the space occupying drilling tools 11 in the well B3 and the well C4 are respectively lifted out, then the space occupying drilling tools 11 in the well C4 are lowered into again, and the height of the cement surface of the well A3 is confirmed by a fish wire hanging measurement method through the cement observation holes 5 arranged on the single-tube three-well base plate 1;

s5, moving the derrick to the well B3, and performing well opening and cementing operation on the well B3;

s6, as shown in figure 4, after the well opening and cementing operation of the well B3 is completed, cement paste waits for more than 24 hours, the derrick is moved to the well C4 during the cement paste waiting for setting, the occupation drilling tool 11 is lifted out, and the height of the cement surface in the well B4 is confirmed by a fish line hanging measurement method through a cement observation hole 5 formed in the single-tube three-well base plate 1;

and S7, moving the derrick to the C well 4, and performing well opening and cementing operation on the C well 4. After the surface drilling method for the triple-barrel well is completed, it is shown in fig. 5.

In this embodiment, the well opening and cementing operation comprises the following steps:

s31, sequentially installing a lifting pipe, a blowout preventer stack and a horn pipe from bottom to top on a wellhead of a corresponding well, and carrying out pressure test on the blowout preventer;

s32, well first-opening operation: drilling to a set well depth by adopting a well section drilling tool combination 19 in a corresponding well, circularly flushing the water-resisting casing pipe 12 through a circulating channel arranged in the occupation drilling tool 11, and taking out the well section drilling tool combination 19;

s33, putting the 11.75-inch surface casing 14 in place in the corresponding well, connecting the surface casing 14 to the hanger 6 of the corresponding well mouth in a sealing manner, and then performing well cementation operation;

s34, after the surface casing 14 is connected with the hanger 6, cutting and recycling redundant parts of the surface casing 14 outside a wellhead, and circularly flushing cement 16 in the water-resisting casing 12 by using drilling fluid through a circulating channel arranged inside the occupation drilling tool 11 during the well cementation operation and within a plurality of hours after the well cementation operation is finished. Specifically, during well cementation, the occupation drilling tool 11 is connected with a high-pressure hose through a variable buckle, large-displacement circulation is continuously carried out through a slurry pump or a well cementation pump, and the highest-displacement circulation is kept for at least twice of the volume of seawater in the water-resisting casing 12 after the well cementation is finished, so that no residual cement slurry exists in the water-resisting casing 12. The space occupying drilling tool 11 has a 2-inch drift diameter inside and a flow passage communicated with the inside on the outer wall, and the flushed seawater can be diffused into the barrel of the riser 12 after entering, so that the inner wall of the riser 12 is clean and free of cement 16.

In addition, two rubber seals 7 are arranged between the hanger 6 of the occupying drilling tool 11 and a 36-inch base plate, the drift diameter is 2 inches, the top is 410-buckled, the occupying drilling tool can be connected with a conventional 5-inch drill rod 8, and the occupying drilling tool 11 can be flushed by connecting a high-pressure hose through overlock, buckle changing and the like during well cementation operation and using a slurry pump or a well cementation pump; the first section of the lifting pipe connected with the single-cylinder three-well base plate 1 is an improved trimming lifting pipe, and the connecting flange plate does not interfere with the hanger 6 of the occupying drilling tool 11; the surface layer casing 14 is a non-joint hoop casing or a joint hoop casing with guide angles arranged above and below the joint hoop; the phenomenon that the sleeve pipe is hung with the adjacent well sleeve pipe in a blocking mode during the casing pipe descending process is avoided; after the surface casing 14 in each well is put in place, a 11.75-inch casing four-way is correspondingly arranged on the base plate and connected with a surface casing 17, the surface casing 14 in the well A is correspondingly connected with a well casing four-way 15, the surface casing in the well B is correspondingly connected with a well casing four-way 17, and the surface casing 14 in the well C is correspondingly connected with a well casing four-way 18; this belongs to the prior art and need not be described in detail.

The space occupying drilling tool 11 sequentially comprises the following components from bottom to top: 14.25 inch plugs + (5 inch drill pipe +14.25 inch separation string +5 inch drill pipe) x a plurality of groups of 1-2 + hangers +5 inch drill pipes; wherein, the inner parts of the plug 10 and the separation string 9 are both provided with 2-inch drift diameters which can form a circulation channel; the lower position of a plug 10 in the occupation drilling tool 11 is positioned inside a riser 12, and the distance between the lower position and the bottom of the riser 12 is less than 2 m; that is, the lower position of the water-proof casing pipe is lower than the lower position of the plug, so that the plug cannot extend out of the water-proof guide pipe, otherwise, the position occupied by the plug cannot be occupied, and meanwhile, if the plug extends out of the water-proof guide pipe, the leakage of the water-proof guide pipe out of the stratum is easily caused. In the space occupying drilling tool 11, the distance between the separation strings 9 in two adjacent separation connecting structures is less than 20 meters; the length of the largest part of the outer diameter of the separator string 9 is 30. The separation string 9 is a reinforced separation string 9 which is a variable diameter cylinder with two thin ends and a thick middle part, wherein the maximum outer diameter of the middle part is a cylinder, the diameter of the bottom surface of the cylinder is 14.25 inches, and the height is about 30cm or 30 cm; this ensures that the spacer strings 9 of the same height in adjacent well sites overlap each other more easily to achieve the effect of space occupation.

The well section drilling assembly 19 is: 13+ motor + MWD + non-magnetic drill collar + centralizer + jar + heavy drill rod + drill rod of 14 inch roller bit; the drill rod in the well section drilling tool assembly and the drill rod in the occupying drilling tool are generally the same drill rod; and starting sliding drilling and deflecting after a 14-inch well section is drilled to a motor corner and a 36-inch water-resisting casing pipe 12 is produced, continuously drawing a line to mark a deflecting direction after an angle difference is measured from the combination drilling tool, and separating the periphery of the well from adjacent well holes as soon as possible according to a designed track after MWD magnetic interference disappears.

The fishing line hanging measurement method comprises the following steps: use the fish tape to connect the plummet, transfer the plummet to meeting through cement observation hole 5 and hinder, measure the fish tape length of putting in, calculate cement stopper face degree of depth according to putting in fish tape length, its computational formula is: the depth of the cement plug surface is equal to the length of the thrown fishing line plus the distance from the single-cylinder three-well base plate 1 to the surface of the rotating disc. The face of the rotary table is the upper surface of the rotary table on the well table and belongs to a known and determined reference surface in the field.

In the 36-inch water-resisting casing 12 with smaller size and stronger strength, the drilling method of the single-barrel three-well is realized by skillful structural design and method steps and by matching with the effective occupation effect of the 14.25-inch separation string 9 in the uniquely-designed occupation drilling tool 11, 3 wellbores of 1 wellbore are independently closed-circuit operated without mutual interference, the well distribution density in unit area is increased, the utilization rate of the notch is fully improved, the pressure of shortage of the offshore oilfield exploitation notch is relieved, and the exploitation cost is greatly reduced.

In addition, the operation of three downhole surface casing 14 can be completed more safely and efficiently by using the surface casing 14 without the joint hoop; and the occupation drilling tool 11 is washed during and after well cementation, the occupation drilling tool 11 is taken out, the torque of the occupation drilling tool is released, the occupation drilling tool 11 is prevented from being twisted or dislocated, and the safety of a shaft can be ensured.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.