Two-way Cycle relay-type coal seam drilling methodTechnical field
The present invention relates to CBM Drilling field of engineering technology, particularly relate to a kind of Two-way Cycle relay-type coal seam drilling method.
Background technology
At present, in CBM exploration and development, the mode that domestic and international drilling technology generally all adopts brill horizontal branch well and mining well to combine.See Fig. 1, brill completion main flow is as follows at present:
1, bore mining well: cement the well after once spud in (hereinafter referred to as " one opens ") bores completion, setting of casing, then secondary spuds in after (opening hereinafter referred to as two) bores completion, setting of casing and cements the well, and expands cave, coal seam afterwards; 2, bore horizontal branch well, setting of casing before entering horizontal segment is also cemented the well, then makes a call to one section of horizontal bare hole well with drilling rod tail band drill bit, by directional technology through after mining straight well, coal seam water plane is beaten the Multilateral Wells of varying number; 3, cementing plug, envelope horizontal branch well well head; 4, mining down-hole pump is utilized, draining and production coal gas.
In said method, mining well mainly plays two effects: one is draining and production coal gas after finishing drilling, and two is air injections in brill horizontal branch well process, assists drilling fluid to take sand and underbalance.This method leaning on the gas injection of mining well to increase circulation prop-carrying capacity can cause the instability of well head pressure and returning fluid, and the risk of aggravation ickings precipitation and bit freezing, facts have proved larger side effect.Through data statistics, in 48 mouthfuls of Multilateral Wells that North China Oilfield company completes over nearly 5 years, only have 14 mouthfuls smoothly, have 14 mouthfuls to collapse and bury drilling tool accident, expense about 20,000,000 RMB is amounted in loss.Cause of accident is mainly as follows: 1, coal seam buried depth shallow (vertical depth < 700m), poor diagenetic grade, and easily collapse block, and this is natural quality; 2, spud in brill bore hole process in horizontal branch well third time, due to annular space between drilling rod sleeve pipe large (spacing 33.0mm), it is low that drilling fluid returns speed, when ickings concentration height, be not enough to whole ickings to recycle well head, cause ickings to block annular space, in addition coal seam bearing capacity is very low again, very easily leaked by pressure, cause well head to lose and return, ickings is understood rapid precipitation and buries dead drilling tool; 3, during mining well air injection, except forming mixed gas drilling fluid, reducing in well except back pressure (i.e. underbalance) effect, also expand by gas itself and help take sand.But, because the bore hole borehole wall is irregular, form air cavity at big hole place, when pressure is low can not with drilling fluid mixed, pressure discharges suddenly after reaching certain value, there will be gas injection pressure and well head returns output cyclic fluctuation, thus exacerbates hole collapse and bit freezing.
Summary of the invention
The object of this invention is to provide a kind of coal seam drilling method of the exploration and development operation for coal bed gas, to solve, mining well air circulation is unstable and annular space is large, return the problem that speed is low and prop-carrying capacity is weak, the impact of easily collapsing in mining well gas injection coal seam can be eliminated again simultaneously, reduce or stop lock of tool drilling generation.
For this reason, technical scheme of the present invention is as follows:
A kind of Two-way Cycle relay-type coal seam drilling method, comprises the following steps:
(1) mining well is bored: well cementation after spudding in brill completion, setting of casing at twice, expansion cave, coal seam;
(2) bore horizontal branch well: by twice brill completion of spudding in, after second time spuds in finishing drilling, lower bilayer sleeve, makes inner layer sleeve be suspended on outer layer sleeve interior and placed in the middle, and the end of inner layer sleeve 0.5 ~ 10m more than the casing shoe of outer layer sleeve; Third time spud in creep into time, Two-way Cycle relay-type is relied on to take sand, walk around mining well, after completing horizontal branch well construction, drill through described mining well, wherein, described Two-way Cycle relay-type takes sand: while drilling rod feed liquor, from feed liquor between described bilayer sleeve, return on after the drilling fluid between bilayer sleeve arrives bottom sleeve footwear and enter between drilling rod and described inner layer sleeve, together with after mixing with drilling circulation liquid, recycle well head;
(3) shut-in well and operation: cementing plug, envelope horizontal branch well well head, utilizes mining down-hole pump, draining and produces coal gas.
Preferably, in brill mining well process, first time spuds in and adopts the drilling well of φ 311.15mm drill bit, and after completion, lower φ 244.5mm sleeve pipe, makes cementing concrete return to ground afterwards; Second time is spudded in and is adopted the drilling well of φ 215.9mm drill bit, and lower φ 177.8mm sleeve pipe after completion, wherein coal seam section uses glass reinforced plastic sleeve, and cementing concrete returns to 200m high, descends drill bit afterwards, and in Chu Kuo cave, coal seam to diameter 0.4 ~ 0.7m, then coal seam section is buried in back-up sand.
Preferably, bore in Completion Operations at horizontal branch well, first time spuds in and adopts the drilling well of φ 444.5mm drill bit, lower φ 339.7mm sleeve pipe after completion, and cementing concrete returns to ground; Second time is spudded in and is adopted the drilling well of φ 311.15mm drill bit, kickoff point (KOP) 50 ~ 600m, the outer layer sleeve of lower φ 244.5mm, cementing concrete is minimum to be returned to 200m high, descends more than the inner layer sleeve of φ 177.8mm to the casing shoe of described φ 244.5mm sleeve pipe 0.5 ~ 10m afterwards, makes it placed in the middle but do not cement the well, only use as circulation, to replace mining well method of gas injection, at the next centralizer of every 3 inner layer sleeves of straight well section, at the next centralizer of every 1 inner layer sleeve of gradient section; Third time spuds in and adopts the drilling well of φ 152.4mm drill bit.
Boring method of the present invention, owing to adding internal layer small casing, many liquid phase circulation passages, in addition original drilling rod circulation, just defines Two-way Cycle more than casing shoe.Rely on the similar relay of Two-way Cycle effect equally to accelerate to return from after the ickings arrival casing shoe of horizontal bare hole section, thus improve the stability of drilling well returning fluid and return output, increase prop-carrying capacity, reduce or eliminate the generation of lock of tool drilling.Owing to taking sand without mining well air assisted, first walking around mining well (later stage is break-through again) when creeping into, doing so avoids the impact that in the cyclic process of mining well, ickings collapses, more ensure that and creep into safely and fast.
Accompanying drawing explanation
Fig. 1 is existing drilled well bore structural representation;
Fig. 2 is the drilled well bore structural representation got out by method of the present invention.
Detailed description of the invention
Two-way Cycle relay-type coal seam drilling method of the present invention is divided into following three phases:
(1) mining well is bored: well cementation after spudding in brill completion, setting of casing at twice, expansion cave, coal seam;
(2) bore horizontal branch well: by twice brill completion of spudding in, after second time spuds in finishing drilling, lower bilayer sleeve, make inner layer sleeve be suspended on outer layer sleeve interior and placed in the middle, and the end of inner layer sleeve is at the above 0.5-10m of the casing shoe of outer layer sleeve; Walk around described mining well when third time spuds in and creeps into, be not first communicated with, after completing horizontal branch well construction, drill through described mining well;
(3) shut-in well and operation: after tripping out inner layer sleeve, at the suitable well section cementing plug of outer layer sleeve, shutoff horizontal branch well well head, utilizes mining down-hole pump, draining and produces coal gas.
Fig. 2 is a specific embodiment of the present invention, is described in further detail method of the present invention below in conjunction with Fig. 2.For clarity sake illustrating with being convenient to, having marked corresponding drill bit and casing size in the drawings.
As shown in Figure 1, Two-way Cycle relay-type coal seam drilling method is divided into following three phases:
(1) the brill completion of mining well:
One opens: adopt drilling fluid, the drilling well of φ 311.15mm drill bit, lower φ 244.5mm sleeve pipe, cementing concrete returns to ground;
Two open: adopt drilling fluid, the drilling well of φ 215.9mm drill bit, lower φ 177.8mm sleeve pipe, and wherein coal seam section uses glass reinforced plastic sleeve, and cementing concrete returns to 200m high, lower drill bit, and in Chu Kuo cave, coal seam, diameter is about φ 0.7m, and coal seam section is buried in back-up sand afterwards.
(2) horizontal branch well bores completion:
One opens: adopt drilling fluid, the drilling well of φ 444.5mm drill bit, lower φ 339.7mm sleeve pipe, cementing concrete returns to ground;
Two open: adopt drilling fluid, the drilling well of φ 311.15mm drill bit, kickoff point (KOP) 400m, lower φ 244.5mm outer layer sleeve, cementing concrete returns to 200m, descend the inner layer sleeve of φ 177.8mm to the above 2m of casing shoe of φ 244.5mm outer layer sleeve afterwards, in straight well section, the next centralizer of every 3 inner layer sleeves, at the next centralizer of every 1 inner layer sleeve of gradient section;
Three open (third time spuds in): adopt drilling fluid, the drilling well of φ 152.4mm drill bit, rely on Two-way Cycle relay-type to take sand, walk around mining well, bore Multilateral Wells, finally drill through mining well.Wherein, described Two-way Cycle relay-type is taken sand and is: from drilling rod feed liquor, (liquid inlet volume is Q1) while, from feed liquor between described bilayer sleeve, (liquid inlet volume is Q2), return on after the drilling fluid between bilayer sleeve arrives bottom sleeve footwear and enter between drilling rod and described inner layer sleeve, together with after mixing with drilling circulation liquid, recycle well head.
(3) shut-in well and operation: cementing plug, envelope horizontal branch well well head.Utilize mining down-hole pump, draining and production coal gas.
Below in conjunction with specific embodiments method of the present invention is illustrated.Concrete data in above-described embodiment are only for illustrative purposes, and can not be used for limiting protection scope of the present invention.The corresponding improvement that those skilled in the art does according to aim of the present invention is all included in right of the present invention.