CN104265215A - Method for reducing kill casing pressure by using well site reserve mud - Google Patents

Abstract

The invention discloses a method for reducing kill casing pressure by using well site reserve mud. The method comprises the following steps: S1, solving formation pressure Pb by using original drilling fluid density Pm and well shutdown stand pipe pressure Pd; S2, calculating required weighted drilling fluid density Pm1 according to the formation pressure Pb; S3, calculating maximum casing pressure value Pam by using invasion gas volume Vb, the formation pressure Pb and drilling bushing annular capacity Ct; S4, calculating well site reserve mud height hmr required for reducing the casing pressure value to be below a safety valve according to the maximum casing pressure value Pam and the well site reserve mud density Pmr; S5, designing kill rate Qkill according to rate pressure of a pump and pumping the well site reserve mud; S6, preparing the weighted drilling fluid, and replacing the well site reserve mud in the annulus to finish kill. The method has the beneficial effects that the kill waiting time can be reduced, the wellhead casing pressure is reduced, safe and quick kill is realized and the method is easy to implement and convenient to construct.

Description

A kind of method utilizing well site to lay in mud reduction kill-job casing pressure

Technical field

The present invention relates to kill-job technical field, particularly a kind of method utilizing well site to lay in mud reduction kill-job casing pressure.

Background technology

Kill-job be in drilling process due to after pressure system disequilibrium generation overflow in stratum-pit shaft, in well, pump into the drilling fluid of certain density, the process of restoration and reconstruction stratum-wellbore pressure balance.At present, conventional Well Killing method has driller's method (two step control methods) and engineer's method (wait and weight method).Driller's method kill-job divides two circulating cycles to carry out, and the first circulating cycle adopted former density circulation of drilling fluid to go out in annular space by the drilling fluid of gas cut; Second circulating cycle pumped into the weighted drilling fluid of trying to achieve by closing well standpipe pressure and displaces former density drilling fluid in pit shaft, thus recovered to set up wellbore pressure system balancing.And engineer's method kill-job is after overflow closing well, strata pressure is tried to achieve according to closing well standpipe pressure, after the drilling fluid of good required kill-job density to be prepared, discharge by a circulating cycle well killing method that gas cut drilling fluid recovers to set up pit shaft-formation pressure system balance simultaneously.

But no matter conventional Well Killing method is driller's method or engineer's method, discharge in circulation in the process of invasion gas, casing pressure all can raise gradually.When Gas top arrives well head, casing pressure reaches maximum value, is generally 2-3 times of casing pressure shut-in.In the pressure of so high cover, weak formation (casing shoe place) may be leaked by pressure, causes down-hole complex accident; The casing pressure of continuous rising also may exceed the bearing capacity of ground installation, causes security incident.So the well killing method of surface casing pressure when mud reduces kill-job is laid in the well site that utilizes worked out, to the minimizing kill-job stand-by period, improve kill-job efficiency, reduce kill-job risk, increase kill-job success rate and play an important role.

Summary of the invention

The object of the invention is to the shortcoming overcoming prior art, there is provided that short, the easy construction of a kind of stand-by period, risk are low, utilize well site to lay in method that mud reduces kill-job casing pressure, reduce the kill-job stand-by period, reduce the too high casing pressure value occurred in conventional Well Killing Process, reduce kill-job risk, belong to a kind of overweight density well killing method.

Object of the present invention is achieved through the following technical solutions: a kind of method utilizing well site to lay in mud reduction kill-job casing pressure, and it comprises the following steps:

S1, utilize former drilling fluid density ρ _mwith closing well standpipe pressure P _dobtain strata pressure P _b;

S2, base area stressor layer P _bcalculating required weighted drilling fluid density is ρ _m1;

S3, utilization invasion gas volume V _b, strata pressure P _bwith drilling rod casing annulus volume C _tcalculate the highest casing pressure value P _am;

S4, the highest casing pressure value P of basis _amwith well site deposit mud density ρ _mr, calculate and casing pressure value be reduced to the required well site deposit mud height h of below safety value _mr;

S5, according to the rated pressure of pump design kill rate Q _kill-job, pump into well site deposit mud;

S6, the weighted drilling fluid density p calculated according to step S2 _m1preparation weighted drilling fluid, and replace out deposit mud in well site in annular space with weighted drilling fluid, complete kill-job.

Described step S1 application conventional Well Killing is theoretical, calculates strata pressure size, that is:

P _b＝P _d+ρ _mgH

P in formula _bfor strata pressure, MPa;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density, g/cm ³;

H is well depth, m.

Described step S2 is theoretical according to conventional Well Killing, utilizes strata pressure P _bcalculate required weighted drilling fluid density p _m1:

${\mathrm{\ρ}}_{m1}=\frac{P_b}{H}=\frac{{\mathrm{\ρ}}_m\mathrm{gH}+P_d}{H}.$

Described step S3 calculates the maximum casing pressure P occurred in Well Killing Process according to the equation of gas state _am:

$P_{\mathrm{am}}=\frac{P_d+\sqrt{P_d^2+\frac{4z_a{T}_a{\mathrm{\ρ}}_m{P}_b{V}_b}{z_b{T}_b{C}_t}}}{2}$

$C_t=\frac{\mathrm{\π}}{4}(d_t^2-d_b^2)$

T _b＝T _a+G _gH

Z in formula _a, z _bbe respectively the Gas Compression Factor in well head, shaft bottom, determined by compressibility factor domain;

T _a, T _bthe temperature in well head, shaft bottom respectively, K;

G _gfor geothermal gradient, K/m;

V _bfor invasion gas volume, i.e. kill-job liquid pool volume recruitment, m ³;

C _tfor drilling rod casing annulus volume, m ³/ m;

D _tfor casing inner diameter, m;

D _bfor drilling rod external diameter, m;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density, g/cm ³;

P _bfor strata pressure, MPa.

Described step S4 comprises calculating, and to pump at ring traffic altitude be h _mrwell site deposit mud after casing pressure, according to designed casing pressure value counter push away deposit mud height, its calculating formula is:

$h_{\mathrm{mr}}=\frac{P_b-x{P}_{\mathrm{am}}-{\mathrm{\ρ}}_{m}g{L}_v-{\mathrm{\ρ}}_{m1}g(H-h_g-L_v)}{({\mathrm{\ρ}}_{\mathrm{mr}}-{\mathrm{\ρ}}_{m1})g},$

$L_v=\frac{\mathrm{\π}(d_d^2{H}_d+d_p^2{H}_p)}{4C_t};$

In formula, x is safety factor, and value is between 0 ~ 1;

P _bfor strata pressure, MPa;

P _amfor the maximum casing pressure value occurred in conventional Well Killing Process, MPa;

ρ _mrfor well site deposit mud density, g/cm ³;

H _mrfor well site deposit mud height, m;

ρ _mfor former drilling fluid density, g/cm ³;

L _vfor the height of drilling rod volume in annular space, m;

D _dfor drilling rod internal diameter, m;

H _dfor run of steel, m;

D _pfor drill collar internal diameter, m;

H _pfor drill collar length, m;

ρ _m1for weighted drilling fluid density, g/cm ³;

H _gfor the height of invasion gas when well head, m.

The present invention has the following advantages: the present invention is reducing by well site deposit mud the casing pressure " spike " occurred in conventional Well Killing Process, reduce in Well Killing Process and can reduce the kill-job stand-by period, reduce surface casing pressure, reduction conventional Well Killing leakage of thin layer (casing shoe), casing pressure exceed ground installation safe pressure value equivalent risk, reduce the risk that in Well Killing Process, leakage and wellhead equipment damage, stand-by period is short, thus reach the object of kill-job safely and fast, and the present invention draw materials convenient and swift, be easy to realize, easy construction.

Accompanying drawing explanation

Fig. 1 is the structural representation of physical model of the present invention

Fig. 2 is for being conventional Well Killing method casing pressure curve (engineer's method)

Fig. 3 is for being utilize well site to lay in mud lubrication casing pressure curve

In figure, 1-drill string, 2-well.

Detailed description of the invention

Below in conjunction with accompanying drawing, the present invention will be further described, and protection scope of the present invention is not limited to the following stated:

The present invention is by setting up a physical model utilizing the casing pressure value during deposit mud reduction kill-job of well site to change as the embodiment be further elaborated the present invention: its physical model as shown in Figure 1, comprises drill string 1 and well 2; Suppose that invasion gas is that entirety is upwards migrated, and with mud without relative sliding, namely along with gas is upwards migrated, the mud on gas column is ejected annular space; The foundation of this model is conducive to analyzing in Well Killing Process, and the change of casing pressure value, is convenient to accurately control casing pressure.

Utilize well site to lay in a method for mud reduction kill-job casing pressure, it comprises the following steps:

S1, utilize former drilling fluid density ρ _mwith closing well standpipe pressure P _dobtain strata pressure P _b;

Application conventional Well Killing is theoretical, calculates strata pressure size, that is:

P _b＝P _d+ρ _mgH

P in formula _bfor strata pressure, MPa;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density g/cm ³;

H is well depth, m;

P in formula _d, ρ _mall obtain by measuring with the numerical value of H.

S2, theoretical according to conventional Well Killing, utilize strata pressure P _bcalculate required weighted drilling fluid density p _m1:

${\mathrm{\ρ}}_{m1}=\frac{P_b}{H}=\frac{{\mathrm{\ρ}}_m\mathrm{gH}+P_d}{H}$

ρ in formula _m1for weighted drilling fluid density, g/cm ³;

P _bfor strata pressure, MPa;

H is well depth, m;

ρ _mfor former drilling fluid density, g/cm ³;

P _dfor closing well standpipe pressure, MPa;

P _d, ρ _mall obtain by measuring with the numerical value of H.

S3, utilization invasion gas volume V _b, strata pressure P _bwith drilling rod casing annulus volume C _tcalculate the highest casing pressure value P _am;

Suppose that invasion gas entirety is upwards migrated.The maximum casing pressure value P occurred in Well Killing Process is calculated according to the equation of gas state _am:

$P_{\mathrm{am}}=\frac{P_d+\sqrt{P_d^2+\frac{4z_a{T}_a{\mathrm{\ρ}}_m{P}_b{V}_b}{z_b{T}_b{C}_t}}}{2}$

$C_t=\frac{\mathrm{\π}}{4}(d_t^2-d_b^2)$

T _b＝T _a+G _gH

Z in formula _a, z _bbe respectively the Gas Compression Factor in well head, shaft bottom, determined by compressibility factor domain;

T _a, T _bthe temperature in well head, shaft bottom respectively, K;

G _gfor geothermal gradient, K/m;

V _bfor invasion gas volume, i.e. kill-job liquid pool volume recruitment, m ³;

C _tfor drilling rod casing annulus volume, m ³/ m;

D _tfor casing inner diameter, m;

D _bfor drilling rod external diameter, m;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density, g/cm ³;

P _bfor strata pressure, MPa.

T in formula _a, V _b, d _t, d _b, P _dand ρ _mnumerical value all by measure obtain.

S4, the highest casing pressure value P of basis _amwith well site deposit mud density ρ _mr, calculate and casing pressure value be reduced to the required well site deposit mud height h of below safety value _mr;

Consider casing shoe place formation fracture pressure and wellhead assembly bearing capacity, lay in utilizing well site the highest casing pressure value occurred in mud lubrication process and be set as xP _am, x value 0-1;

This step comprises calculating, and to pump at ring traffic altitude be h _mrwell site deposit mud after casing pressure, according to designed casing pressure value counter push away deposit mud height, its calculating formula is:

$h_{\mathrm{mr}}=\frac{P_b-x{P}_{\mathrm{am}}-{\mathrm{\ρ}}_{m}g{L}_v-{\mathrm{\ρ}}_{m1}g(H-h_g-L_v)}{({\mathrm{\ρ}}_{\mathrm{mr}}-{\mathrm{\ρ}}_{m1})g}$

$L_v=\frac{\mathrm{\π}(d_d^2{H}_d+d_p^2{H}_p)}{4C_t}$

In formula, x is safety factor, and value is between 0 ~ 1;

P _bfor strata pressure, MPa;

P _amfor the maximum casing pressure value occurred in conventional Well Killing Process, MPa;

ρ _mrfor well site deposit mud density, g/cm ³;

H _mrfor well site deposit mud height, m;

ρ _mfor former drilling fluid density, g/cm ³;

L _vfor the height of drilling rod volume in annular space, m;

D _dfor drilling rod internal diameter, m;

H _dfor run of steel, m;

D _pfor drill collar internal diameter, m;

H _pfor drill collar length, m;

ρ _m1for weighted drilling fluid density, g/cm ³;

H _gfor the height of invasion gas when well head, m;

ρ in formula _mrand ρ _mnumerical value all by measure obtain.

S5, according to the rated operating pressure of pump design kill rate Q _kill-job, pump into well site deposit mud;

P _{rated pressure}>P _{circulating pressure}+ P _d

Therefore, Q _kill-job=(1/3 ~ 1/2) Q _normally

P _dfor closing well standpipe pressure, MPa;

P _{circulating pressure}numerical value by measure obtain.

S6, the weighted drilling fluid density p calculated according to step S2 _m1preparation weighted drilling fluid, pumps into weighted drilling fluid, replaces out deposit mud in well site in annular space, complete kill-job with weighted drilling fluid.

During practical operation, utilize former drilling fluid density ρ _mwith closing well standpipe pressure P _dobtain strata pressure P _b; Utilize strata pressure P _bcalculate required weighted drilling fluid density p _m1; According to invasion gas volume V _b, strata pressure P _bwith drilling rod casing annulus volume C _tobtain the highest casing pressure value P _am; According to P _ammud density ρ is laid in well site _mrand the height L of drilling rod volume in annular space _vobtain well site deposit mud height h _mr; According to the rated pressure design kill rate Q of pump _kill-job, and pump into well site deposit mud; According to the weighted drilling fluid density p calculating gained _m1preparation weighted drilling fluid, and pump into pit shaft, replace out deposit mud in well site in annular space with weighted drilling fluid, recover and set up pit shaft-strata pressure balance, completing kill-job.

In the present invention, the physical model setting up casing pressure value change when utilizing well site deposit mud reduction kill-job comprises following content: suppose that invasion gas is overall migration, and with mud without relative sliding; And ignore the insulating liquid pumped into before well site deposit mud and weighted drilling fluid; The physical model set up as shown in Figure 1.

In the present invention, in described step S4, determine required well site deposit mud height h _mrcomprise following content:

Gas meets the equation of gas state: PV=znRT

Then $\frac{P_a{V}_a}{z_a{T}_a}=\frac{P_b{V}_b}{z_b{T}_b}$

In formula

P _afor casing pressure, MPa

P _bfor strata pressure, MPa;

V _afor gas migration is to volume during well head, m ³;

V _bfor invasion gas volume, m ³;

Z _afor well head Gas Compression Factor;

Z _bfor the Gas Compression Factor in shaft bottom;

Gas migration is to gas column height during well head:

$h_g=\frac{V_a}{C_t}$

H in formula _gfor gas migration is to gas column height during well head;

V _afor gas migration is to volume during well head, m ³;

C _tfor drilling rod casing annulus volume, m ³/ m.

Required well site deposit mud height gauge formula:

$h_{\mathrm{mr}}=\frac{P_b-x{P}_{\mathrm{am}}-{\mathrm{\ρ}}_{m}g{L}_v-{\mathrm{\ρ}}_{m1}g(H-h_g-L_v)}{({\mathrm{\ρ}}_{\mathrm{mr}}-{\mathrm{\ρ}}_{m1})g}$

In formula, x is safety factor, and value is between 0 ~ 1;

P _bfor strata pressure, MPa;

P _amfor the maximum casing pressure value occurred in conventional Well Killing Process, MPa;

ρ _mrfor well site deposit mud density, g/cm ³;

H _mrfor well site deposit mud height, m;

ρ _mfor former drilling fluid density, g/cm ³;

L _vfor the height of drilling rod volume in annular space, m;

ρ _m1for weighted drilling fluid density, g/cm ³;

H _gfor the height of invasion gas when well head, m.

As shown in the physical model of foundation, draw surface casing pressure:

P _al＝P _b-ρ _mrgh _mr-ρ _mgh _m-ρ _mggh _g

P in formula _bfor strata pressure, MPa;

ρ _mrfor well site deposit mud density, g/cm ³;

H _mrfor well site deposit mud height, m;

H _mfor former drilling fluid height, m;

ρ _mfor former drilling fluid density, g/cm ³;

ρ _mgfor invasion gas density, g/cm ³;

H _gfor the height of invasion gas when well head, m.

Well site deposit mud height needed for calculating according to designed casing pressure.

Conventional Well Killing casing pressure curve (engineer's method) as shown in Figure 2 and the well site that utilizes as shown in Figure 3 are laid in mud lubrication casing pressure curve, puts together, intuitively contrast.In figure, t ₁that kill mud arrives drill bit place; t ₂that invasion gas top arrives well head; t ₃that gas discharges well completely; t ₄weighted drilling fluid (Fig. 2)/well site deposit mud (Fig. 3) arrives well head.

Claims (5)

1. utilize well site to lay in a method for mud reduction kill-job casing pressure, it is characterized in that: it comprises the following steps:

S1, utilize former drilling fluid density ρ _mwith closing well standpipe pressure P _dobtain strata pressure P _b;

S2, base area stressor layer P _bcalculating required weighted drilling fluid density is ρ _m1;

S3, utilization invasion gas volume V _b, strata pressure P _bwith drilling rod casing annulus volume C _tcalculate the highest casing pressure value P _am;

S4, the highest casing pressure value P of basis _amwith well site deposit mud density ρ _mr, calculate and casing pressure value be reduced to the required well site deposit mud height h of below safety value _mr;

S5, according to the rated pressure of pump design kill rate Q _kill-job, pump into well site deposit mud;

S6, the weighted drilling fluid density p calculated according to step S2 _m1preparation weighted drilling fluid, and replace out deposit mud in well site in annular space with weighted drilling fluid, complete kill-job.

2. a kind of method utilizing well site to lay in mud reduction kill-job casing pressure according to claim 1, is characterized in that: described step S1 application conventional Well Killing is theoretical, calculates strata pressure size, that is:

P _b＝P _d+ρ _mgH

P in formula _bfor strata pressure, MPa;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density g/cm ³;

H is well depth, m.

3. a kind of method utilizing well site to lay in mud reduction kill-job casing pressure according to claim 1, is characterized in that: described step S2 is theoretical according to conventional Well Killing, calculates required weighted drilling fluid density p _m1:

${\mathrm{\ρ}}_{m1}=\frac{P_b}{H}=\frac{{\mathrm{\ρ}}_m\mathrm{gH}+P_d}{H}.$

4. a kind of method utilizing well site to lay in mud reduction kill-job casing pressure according to claim 1, is characterized in that: described step S3 calculates the maximum casing pressure P occurred in Well Killing Process according to the equation of gas state _am:

$P_{\mathrm{am}}=\frac{P_d+\sqrt{P_d^2+\frac{4z_a{T}_a{\mathrm{\ρ}}_m{P}_b{V}_b}{z_b{T}_b{C}_t}}}{2};$

$C_t=\frac{\mathrm{\π}}{4}(d_t^2-d_b^2);$

T _b＝T _a+G _gH；

Z in formula _a, z _bbe respectively the Gas Compression Factor in well head, shaft bottom, determined by compressibility factor domain;

T _a, T _bthe temperature in well head, shaft bottom respectively, K;

G _gfor geothermal gradient, K/m;

V _bfor invasion gas volume, i.e. kill-job liquid pool volume recruitment, m ³;

C _tfor drilling rod casing annulus volume, m ³/ m;

D _tfor casing inner diameter, m;

D _bfor drilling rod external diameter, m;

P _dfor closing well standpipe pressure, MPa;

ρ _mfor former drilling fluid density g/cm ³;

P _bfor strata pressure, MPa.

5. a kind of utilize well site to lay in method that mud reduces kill-job casing pressure according to claim 1, is characterized in that: described step S4 comprises calculating, and to pump at ring traffic altitude be h _mrwell site deposit mud after casing pressure, according to designed casing pressure value counter push away deposit mud height, its calculating formula is:

$h_{\mathrm{mr}}=\frac{P_b-x{P}_{\mathrm{am}}-{\mathrm{\ρ}}_{m}g{L}_v-{\mathrm{\ρ}}_{m1}g(H-h_g-L_v)}{({\mathrm{\ρ}}_{\mathrm{mr}}-{\mathrm{\ρ}}_{m1})g}$

P in formula _bfor strata pressure, MPa;

X is safety factor, and value is between 0 ~ 1;

P _amfor the maximum casing pressure value occurred in conventional Well Killing Process, MPa;

ρ _mrfor well site deposit mud density, g/cm ³;

H _mrfor well site deposit mud height, m;

ρ _mfor former drilling fluid density g/cm ³;

L _vfor the height of drilling rod volume in annular space, m;

ρ _m1for weighted drilling fluid density, g/cm ³;

H _gfor the height of invasion gas when well head, m.