CN105178869A - Method for calculating size combination of nozzle of drill bit for petroleum drilling - Google Patents

Abstract

The invention discloses a method for calculating size combination of nozzles of a drill bit for petroleum drilling; optimal solutions of di and ni are obtained according to constraint conditions; i is not smaller than 0; m is not smaller than i; a nozzle size nearest the optimal solutions is obtained; the constraint conditions are as follows: 1) di is not smaller than a1 and not greater than a2; and i is not smaller than 0 and not greater than m; 2) di+1-di is not smaller than 0 and not greater than bi; and i is not smaller than 1 and not greater than m; 3) the summation of ni equals to n with i ranging from 1 to m; 4) delta S=Sd-Sopt bigger than 0, wherein Sd and Sopt are described in the description, m and n represent that n nozzles have m sizes; di is the diameters of the nozzles with the ith size and is ranked according to that the diameter di is gradually reduced with the increment of i; ni is the number of the nozzles with the ith size; a1 and a2 are experience numerical values for limiting the nozzle size; bi is an experience numerical value for limiting the nozzle size difference; pd is the drilling liquid density; and pbd is the designed maximum pressure drop of the drill bit. The method can accurately and quickly obtain an optimal nozzle size combination.

Description

The jet size combination computational methods of oil drilling drill bit

Technical field

The present invention relates to oil drilling technology field, in particular to a kind of jet size combination computational methods of oil drilling drill bit.

Background technology

Practice shows, in larger the pressure of the drill and the range of speeds, reduces nozzle diameter, increase jet jet velocity can significantly improve rate of penetration and footage per bit.Adopt jet bit to creep into compared with normal drill bit, in soft formation, footage per bit can improve 50% ~ 100%, in hard formation, then can improve 13% ~ 28%; Rate of penetration can improve 15 ~ 30% in soft formation, can improve 14% ~ 21% in hard formation.

In theory, site engineer needs optimum capacity according to situation determination drill bits such as the construction speed of institute's drilling well, drilling parameter, drilling assembly and drilling equipments and optimum nozzle equivalent diameter, and selects the jet size of drill bit to combine.But, in real work, by the impact of site plant ability, normally first rule of thumb determine drilling fluid displacement, then according to drilling assembly and mud property parameter computation cycles pressure consumption, finally by constantly changing jet size combination, ensureing that bit nozzle pressure drop and circulation of drilling fluid are pressed and consuming the rated pressure of sum lower than borehole pump.For saving amount of calculation, also normally creep into demand to ensure that the rated pump pressure of borehole pump can meet simultaneously, it is larger that the combination of jet size that situ of drilling well adopts often is selected, and makes bit hydraulic auxiliary rock ability and alleviate landwaste to hold and press the effect of effect greatly to weaken.

Summary of the invention

Technical problem to be solved by this invention is, provides a kind of method that can obtain optimum nozzle dimension combination accurately and rapidly,

Therefore, technical scheme of the present invention is as follows:

Jet size combination computational methods for oil drilling drill bit, try to achieve d under Δ S minimum according to constraints _iand n _ioptimal solution, 1≤i≤m, then jet size immediate with described optimal solution, described constraints comprises |:

1)a ₁≤d _i≤a ₂，1≤i≤m；

2)0≤d _i+1-d _i≤b _i，1≤i≤m-1；

3) ${\mathrm{\Σ}}_{i=1}^m{n}_i=n;$

4) Δ S=S _d-S _opt>0, wherein, $S_d=\frac{{\mathrm{\π\Σ}}_{i=1}^m{n}_i{d}_i^2}{4},S_{opt}={\left(\frac{554.4\×{\mathrm{\ρ}}_d\×Q^2}{p_{bd}}\right)}^{0.5};$

Wherein, m and n represents altogether have size in m, d in n nozzle _ibe the diameter of i-th kind of size nozzle and increase sequence successively, n according to increasing diameter with i _ibe the quantity of i-th kind of size nozzle, a ₁and a ₂for limiting the empirical value of jet size, b _ifor limiting the empirical value of nozzle member size difference, ρ _dfor drilling fluid density, p _bdthe maximum pressure proposing meter for drill bit falls, and Q is drilling fluid displacement, and each Parameter units is d _i-mm, a ₁-mm, a ₂-mm, b _i-mm, ρ _d-g/cm ³, b _i-mm, p _bd-MPa, Q-L/s.

In this technical scheme, utilize the instruments such as excel can according to creeping into the nozzle quantity of on-the-spot drill bit for subsequent use, drilling liquid parameter, slush pump rated pressure and DHA and jet size constraints, calculate optimum nozzle dimension combination fast, thus meeting under the condition that slush pump normally works, play the waterpower auxiliary rock-breaking effect of drill bit to greatest extent.

Further, p _bd=p _bmax/ f, p _bmax=p _r-Δ p _cs; Wherein, p _rfor borehole pump rated pump pressure, Δ p _csfor drilling circulation system pressure losses, f is the safety factor rule of thumb set, p _rwith Δ p _csunit is MPa.

In this technical scheme, utilize p _rwith Δ p _csp falls in the maximum pressure calculating drill bit _bmax, utilize a safety factor f to determine final p further _bd, considering a real pump pressure (actual pump pressure during slush pump work) can to a certain extent lower than rated pump pressure p _r, thus ensure that calculating is recorded a demerit more reliable.

Detailed description of the invention

It should be noted that, when not conflicting, the feature in the embodiment of the application and embodiment can combine mutually.

The jet size combination computational methods of oil drilling drill bit according to an embodiment of the invention, 21.59cm drill bit is used for certain well, nozzle number is 5, Φ 17.78/7.14cm drill collar 80m, all the other are Φ 12.7/10.862cm drilling rod, it is 4000m that this drill bit estimates that brill reaches well depth, drilling fluid averag density 1.2g/cm ³, plastic viscosity 20mPas, two NB8-600 pumps.Concrete steps are as follows.

Step one, computation cycles pressure consumption.By the mode of on-the-spot test, measure the cyclic pressure dissipation coefficient inside and outside manifold of ground, drill collar and inside and outside drilling rod respectively, finally trying to achieve cyclic pressure dissipation is 7.77MPa.

Step 2, according to engineering practice determination minimum injection rate Q _minfor 23.93L/s.

Step 3, selects cylinder sleeve diameter according to pump physical condition.For NB8-600 pump, according to the data that " drilling well handbook " provides, can select the cylinder sleeve of 130mm diameter, rated pump pressure is 19.6MPa, rated discharge Q when strokes per minute is 65 times/min _rfor 15.34L/s, when adopting double pump, Q _rfor 30.68L/s.

Step 4, according to on-site actual situations determination drilling fluid displacement.The optimum capacity adopting maximum jet impact force principle to determine, for being 30.76L/s, because the optimum drilling fluid displacement of gained is greater than the rated discharge of slush pump, gets the rated discharge that actual well drilled liquid discharge capacity Q equals slush pump, i.e. 30.68L/s.

Step 5, calculates bit nozzle equivalent aera and diameter.In drilling process, borehole pump is in rated pump pressure duty, the sectional area S under bit nozzle equivalent diameter _jfor

$S_J={\left(\frac{554.4\×{\mathrm{\ρ}}_d\×Q^2}{p_s-{\mathrm{\Δp}}_{cs}}\right)}^{0.5}={\left(\frac{554.4\×1.2\×{30.68}^2}{19.6-7.77}\right)}^{0.5}=230.13{\mathrm{mm}}^2;$

$d_t={\left(\frac{4S_J}{\mathrm{\π}}\right)}^{0.5}=17.12mm;$

The pass of nozzle equivalent diameter and the actual each nozzle diameter of drill bit is

${d_t}^2=\underset{i=1}{\overset{n}{\Σ}}{d_i}^2;$

Wherein, S _jfor the sectional area (mm under nozzle equivalent diameter ²), d _tfor bit nozzle equivalent diameter (mm), Q is drilling fluid actual flow (L/s), P _ssend out pump pressure (MPa) for borehole pump is real and get rated pump pressure value (note: the real actual pump pressure sent out when pump pressure refers to that slush pump works, can to a certain extent lower than rated pump pressure, therefore the bit nozzle equivalent diameter calculated and area less than normal, thus before carrying out programming evaluation, need setting safety factor, suitably increase the nozzle cross-section sum nozzle diameter after optimizing).

Obviously, at known preferred nozzle diameter d _tafter, n the nozzle diameter meeting above formula has Multiple Combination form, and hand computation workload is large and be difficult to the bit hydraulic auxiliary rock effect of determining which kind of jet size combination concrete can be best, illustrates at a certain nozzle equivalent diameter d _twith sectional area S _junder condition, there is multiple solution in jet size combination, and is difficult to judge optimal solution.

Step 6, adopts programming evaluation instrument (such as Excel), adds and solves constraints, calculates the optimum size combination obtaining bit nozzle.

p _bmax＝P _s-Δp _cs＝p _r-Δp _cs＝19.6-7.77＝11.83MPa

p _bd＝p _bmax/f＝11.83/1.5＝7.89MPa

$S_{opt}={\left(\frac{554.4\×{\mathrm{\ρ}}_d\×Q^2}{p_{bd}}\right)}^{0.5}={\left(\frac{554.4\×1.2\×{30.68}^2}{7.89}\right)}^{0.5}=281.85{\mathrm{mm}}^2$

S _d＝π(n ₁d ₁ ²+n ₂d ₂ ²+n ₃d ₃ ²)/4

ΔS＝S _d-S _opt

Solve constraints to comprise:

① $\left\{\begin{array}{c}8\≤d_1\≤18\\ 8\≤d_2\≤18\\ 8\≤d_3\≤18\end{array}\right.,$ For the scope of limits nozzle size, jet size scope can set according to engineer applied actual conditions;

② $\left\{\begin{array}{c}0\≤d_2-d_1\≤2\\ 0\≤d_3-d_2\≤2\end{array}\right.,$ For the difference size between limits nozzle size, can set according to engineer applied actual conditions; ;

3. n ₁, n ₂, n ₃be all be more than or equal to 0 integer, for solving the number of different size nozzle;

4. n ₁+ n ₂+ n ₃=5, for limit solve draw nozzle sum identical with actual nozzle hole number on drill bit;

5. Δ S >=0, for ensureing to solve the Nozzle combination equivalent diameter that the draws optimum nozzle equivalent diameter slightly larger than drill bit, thus within being in rated pump pressure when ensureing slush pump work.

Changing cell comprises d ₁, d ₂, d ₃, n ₁, n ₂, n ₃, object element is Δ S.Solve the value of changing cell under Δ S minimal condition, show that qualified jet size is combined as the dimension combination being bit nozzle.

Utilize the programming evaluation function in Excel, arrange solve object, defined variable and constraint after, try to achieve d ₁=8mm, d ₂=8mm, d ₃=9mm, n ₁=0, n ₂=2, n ₃=3, i.e. 2, the nozzle of 8mm, can be best during 3, the nozzle of 9mm utilize drilling fluid waterpower rinse capability.

The last nozzle specification specified according to handbook, selects and the immediate jet size of 8mm and 9mm, i.e. 2, the nozzle of 8.73mm, 3, the nozzle of 9.53mm.

In sum, content of the present invention is not limited in the above-described embodiment, and those skilled in the art can propose other embodiment within technological guidance's thought of the present invention, but this embodiment all comprises within the scope of the present invention.

Claims (2)

1. jet size combination computational methods for oil drilling drill bit, is characterized in that, try to achieve d under Δ S minimum according to constraints _iand n _ioptimal solution, 1≤i≤m, then jet size immediate with described optimal solution, described constraints comprises |:

1)a ₁≤d _i≤a ₂，1≤i≤m；

2)0≤d _i+1-d _i≤b _i，1≤i≤m-1；

3) ${\mathrm{\Σ}}_{i=1}^m{n}_i=n;$

4) Δ S=S _d-S _opt>0, wherein, $S_d=\frac{{\mathrm{\π\Σ}}_{i=1}^m{n}_i{d}_i^2}{4},S_{opt}={\left(\frac{554.4\×{\mathrm{\ρ}}_d\×Q^2}{p_{bd}}\right)}^{0.5};$

Wherein, m and n represents altogether have m kind size, d in n nozzle _ibe the diameter of i-th kind of size nozzle and increase sequence successively, n according to increasing diameter with i _ibe the quantity of i-th kind of size nozzle, a ₁and a ₂for limiting the empirical value of jet size, b _ifor limiting the empirical value of nozzle member size difference, ρ _dfor drilling fluid density, p _bdthe maximum pressure proposing meter for drill bit falls, and Q is drilling fluid displacement, and each Parameter units is d _i-mm, a ₁-mm, a ₂-mm, b _i-mm, ρ _d-g/cm ³, b _i-mm, p _bd-MPa, Q-L/s.

2. the jet size combination computational methods of oil drilling drill bit according to claim 1, is characterized in that:

p _bd＝p _bmax/f，p _bmax＝p _r-Δp _cs；

Wherein, p _rfor borehole pump rated pump pressure, Δ p _csfor drilling circulation system pressure losses, f is the safety factor rule of thumb set, p _rwith Δ p _csunit is MPa.