RU2646280C2 - Detachable adapter - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: detachable adapter comprises a nipple and a coupling connected to each other by a two-thread cylindrical thread of a large pitch. The average thread diameter is determined by expression D_cp=|(D²+d²-2h²)/2|^0.5. Torque moments of connection tightening meet the conditions T_wa=T_us and T_ua>T_us, where D and d are outer and inner diameters of the adapter; h is the height of the thread profile; T_wa - working torque of adapter threaded connection; T_us - ultimate tightening torque of the drill string threaded connections (σ_z=σ_y); T_ua - ultimate tightening torque of adapter threaded connection (σ_z=σ_y); σ_z - tightening tension in dangerous section of the threaded connection; σ_y - yield strength of the threaded joint material.

EFFECT: providing strength, tightness, and high reliability when drilling and disconnecting the drill string from stuck core tool or bit.

2 dwg, 1 tbl

Description

The invention relates to devices designed to disconnect a drill pipe string from a core bit or drill bit stuck in a well during deep oil and exploration drilling, mainly using a tool complex with a removable core receiver (CCK).

These devices, called disconnect adapters (hereinafter referred to as the adapter), are divided into the following groups according to the principle of action: freely unscrewed; with easily collapsing weak link; hydraulic; combined and universal / 2 /. For the most part, they have a complex structure and therefore do not fit into a very small section of thin-walled drill pipes used with SSC.

The closest analogue adopted for the prototype of the present invention is a widespread freely unscrewable detachable adapter containing a nipple and a coupling connected by a double-thread cylindrical thread of a large pitch, and a bronze ring mounted in the thrust joint of the connection / 1, 2 /. The set of features of the analogue, which coincides with the set of essential features of the invention, are: a nipple and a coupling connected by a double-thread of large pitch.

The prototype design has the following disadvantages.

1. The threaded connection of the adapter is inferior in strength to the threaded connection of the drill string, which is caused by the uneven strength of the dangerous sections of the nipple and the coupling.

Design calculations of the prototype, for example, with an outer diameter of 146 mm, presented on page 11 in / 1 /, showed that the areas of dangerous sections of the nipple and the coupling, respectively, are 3438 and 7475 mm ² , i.e. the nipple is 2.2 times smaller than the coupling. At the same time, the area of the dangerous section of the nipple of the weld-lock ZP-140-57 (GOST 27834) of the drill pipes PV 102x8 (GOST R 50278), which make up the drill string, which includes the adapter, is 5776 mm ² , which is 68% more than in the dangerous section of the adapter nipple. This is due to the fact that the average diameter of the adapter thread is adopted without taking into account the equal strength factor of their component parts - the nipple and the coupling. With the combined action of increased torques and tensile forces in the process of trying to free the drill string from the stuck drill, this circumstance accordingly increases the risk of adapter breakage along the dangerous section of the nipple, and therefore, the probability of failure of the main function of the adapter is to disconnect the drill string.

2. The use of a non-ferrous metal ring in order to reduce the friction coefficient in the abutment joint of the adapter connection limits the creation of the proper preliminary tightening torque of the threaded connection, which reduces its fatigue resistance and tightness / 6 /, since the yield strength of non-ferrous metal (for example, bronze) from of which the ring is made, several times smaller than that of steel. In addition, a slightly tightened adapter connection is prone to self-unscrewing, leading to the loss of a core projectile or bit in the well during tripping. Unfortunately, in the method of calculating the tightening torque recommended on page 27, the authors of / 1 / miss the calculation option that takes into account a sharp decrease in the tightening force of the threaded connection due to the presence of this non-ferrous metal ring in its thrust joint.

The technical problem is to create an adapter that is not inferior in strength and tightness to the threaded joints of the drill string and has high reliability both when drilling and when performing its main function of disconnecting the drill string from a stuck core drill or bit, mainly when drilling using the CCK complex .

To solve this technical problem in the adapter containing the nipple and the coupling, interconnected by a double-thread cylindrical thread of large pitch, the average diameter of the thread is determined by the expression D _cp = | (D ² + d ² -2h ² ) / 2 | ^0.5 , and the tightening torques of its connection meet the conditions M _pn = M _pc and M _pn > M _pc ,

Where:

D and d are the outer and inner diameters of the adapter;

h is the height of the thread profile;

M _RP - working torque of the threaded connection of the adapter;

M _pc - the ultimate tightening torque of the threaded joints of the drill pipe string (σ _s = σ _t );

M _PP - the ultimate tightening torque of the threaded connection of the adapter (σ _s = σ _t );

σ _s - tension in a dangerous section of a threaded connection;

σ _t - yield strength of the material of the threaded connection.

The invention is illustrated in FIG. 1 and FIG. 2.

In FIG. 1 is a drawing of an adapter designed to operate as part of a thin-walled drill string of the CCK complex. Here are depicted: 1 - nipple; 2 - coupling; 3 - rubber ring; 4 - paronite gasket.

In FIG. 2 shows a graph of the coefficient of influence of the preliminary tightening (K _VPZ ) on the endurance limit of the threaded connection on the coefficient of its tightening (K _s = σ _s / σ _t ) / 6 /.

The inventive device allows to solve the technical problem.

Indeed, the condition of equal strength of the threaded connection of the adapter can be represented by the following expression:

Where:

F _osn and F _osm - the dangerous cross-sectional area of the nipple and coupling, respectively.

With an average thread diameter D _sr, both areas can be represented by the following expressions:

Returning to the condition of equal strength (1) and using expressions (2) and (3), we obtain the average diameter of the thread, ensuring equal strength of the dangerous sections of the nipple and the coupling:

where from

An example implementation of the invention

As an example, we will calculate the design of the detachable adapter as applied to the drill string with a diameter of 69.9 mm of the CCK complex with optimal parameters of the threaded joint (see Table 1) according to the patent “Threaded connection of drill pipes” / 3 /.

1. We accept the outer and inner diameters of the adapter the same as that of the outer core pipe with which it is connected, i.e. D = 73 mm and d = 60.3 (see Fig. 1).

Two-thread, trapezoidal profile with an apex angle of 10 °, thread pitch S = 12.7 mm, stroke t = 25.4 mm, thread profile height h = 1.5 mm. The strength and yield strengths of steel of threaded joints of the drill string and adapter are the same: σ _in = 980 MPa and σ _t = 833 MPa.

The average diameter of the thread of the adapter from the expression (4) is equal to:

D _cf = | (73 ² +60.3 ² -2 × 1.5 ² ) / 2 | ^0.5 = 66.935 mm.

Using the average thread diameter, we find the main thread diameters of the nipple and the coupling:

D _pH - The outer diameter of the thread of the nipple is 66.935 + 1.5 = 68.435 mm;

d _pH - The inner diameter of the thread of the nipple is 66.935-1.5 = 65.435 mm;

D _pm - Outer diameter of the thread of the coupling - 66.935 + 1.5 = 68.435 mm;

d _pm - The inner diameter of the thread of the coupling is 66.935-1.5 = 65.435 mm.

Having the outer and inner diameters of the thread, we find the area of dangerous sections:

Nipple F _DOS = (65.435 ² -60.3 ² ) × 0.785 = 506.835 ~ 507 mm ² ;

Couplings F _osm = (73 ² -68.435 ² ) × 0.785 = 506.835 ~ 507 mm ² .

The same values of dangerous cross sections should be obtained from expressions (2) and (3):

At pin F _est = | (66,935-1,5) ² -60.3 ²⁾ | × 0,785 = 506,835 ~ 507 mm ^2;

The coupling F _osm = | 73 ² - (66.935 + 1.5) ² | × 0.785 = 506.835 ~ 507 mm ² ,

which indicates the equal strength of the nipple and the coupling and the validity of the expression / 4 /.

2. The torque of the friction resistance in the thread when it is tightened is determined by the dependence / 5, 6 /:

Where:

Q is the optimal thread tightening force determined by the expression

σ _t - yield strength of steel threaded connections of the adapter and the drill string;

To _s - the tightening coefficient of the threaded connection To _s = σ _s / σ _t (taken for both types of connections To _s = 0.66) / 6 /;

To _p is the coefficient of proportionality of the thread parameters, which is determined by the following dependence / 5, 6 /

K _p = D _cp / 2 (A + μ) / (l-μ),

Where:

n is the number of thread starts;

μ - coefficient of sliding friction (for "steel on steel" with graphite lubricant μ = 0.1);

3. The torque of friction resistance in the outer or inner thrust joints is determined by the dependence / 5 /

Where:

K _article - the proportionality coefficient of the parameters of the thrust joint

The value of k ₀ for the outer joint

Where:

D _p - the diameter of the bore of the end face of the coupling of the threaded connection.

The value of k ₀ for the inner joint

Where:

d _p - the diameter of the groove end of the nipple of the threaded connection

4. The joint tightening torque is equal to the sum of the frictional resistance torques in the thread and in the abutting joints.

The calculation results based on the above dependencies are summarized in table. one.

** Based on the results of bench tests of Drilling Equipment Plant OJSC / 3 / full-scale samples of drill pipe joints, its ultimate bending moment of steel with a temporary resistance of 980 MPA will be M _pre = 980 × 0.4: 8.6 × 6.4 × 2.8 = 817 Nm, where 0.4 is the coefficient of decrease in strength during the fatigue test of a smooth specimen, 6.4 is the coefficient of decrease in the endurance limit due to the concentration of stresses in the thread (K _σ ) _D. Since the compared threaded connections from the point of view of the effect on fatigue differ only in the moment of bending resistance (W _and ), the ultimate bending moment of the adapter, taking into account this difference, will be 980 × 0.4: 8.6 × 8.9 × 2.8 = 1135 Nm .

It should also be noted here that the threaded connection of the adapter is tightened with a torque equal to the limiting torque of the tightening of the threaded joints of the drill string, i.e. 22% percent lower than the optimal value for it (see paragraph 18 of Table 1), and therefore, the drag coefficient will decrease to a value of K _s = 0.66 × 0.78 = 0.51 and, accordingly, K _vpz = 2, 3 (see the graph in FIG. 2). Then, for connecting the adapter M, _pre = 1135 × 2.3 / 2.8 = 932 Nm. Even in this case, the M _{before the} adapter is higher, and therefore, the alternating bending margin is higher than that of the drill string joints (932/817 = 1.14).

*** Since the drill string connections have double-threaded threads, the total torque is both optimal (working) and ultimate (M _pc = 2551 Nm) for them. This is explained by the fact that the area of the inner joint for a double-joint connection (275 mm ² ) was established / 3 / from the condition of creating a stress in it equal to the yield strength of steel (σ _s = σ _t = 833 MPa). For the adapter, in the threaded connection of which there is no internal joint, the optimum tightening force is ensured only due to the external joint, and the voltage in it due to the larger area (464 mm ² ) is 278738/464 = 600 MPa. Therefore, the ultimate tightening force (at σ _t = 833 MPa) and the corresponding ultimate torque of the adapter connection are significantly higher (M _pp = 3105.2 Nm).

**** Tightening force determines the friction forces, the total value of which depends on the number of contacts of the connection parts and does not depend on the area of contacted surfaces. There are three such contacts in the drill string connection, and only two in the adapter connection. Therefore, the total value of the friction force in the adapter connection at a working tightening moment (M _rp ) equal to the limiting moment (M _pp ) for the drill string joints is 1.5 times less (229 × 3/229 × 2 = 1.5), which and ensures the operation of the adapter during the operation to disconnect the drill string from the stuck core drill or bit.

***** The lack of friction forces at the contacts of the adapter connection parts necessary for the formation of a tightening torque equal to the ultimate tightening torque of the drill string joints (M _pc ) is fully compensated by the higher proportional coefficients of the thread K _p and the external contact joint K _st . The first is more than the similar coefficient of the drill string connections by 62% (7.56 against 4.66), and the second by 5% (3.58 against 3.4), and in the first case this is due to the fact that the thread of the adapter connection is three times higher (25,400: 8,466 = 3) than the threads of the drill string joints, and in the second - a large ratio of the outer and inner diameters of the adapter connection.

To seal the threaded connection in the right (with an open inoperative internal joint) part of the adapter (Fig. 1) we install a rubber ring and a paronite gasket.

Before assembling the adapter, its parts (nipple and coupling), as well as the rubber ring, are lubricated with special graphite grease of the R-2/7 / type. Then, a rubber ring and a paronite gasket are installed, and after screwing up by hand, the connection is tightened with a torque M _rp = 2551 Nm, i.e. with a moment equal to the ultimate tightening torque of the threaded joint of the drill string (M _pc ). The assembled and tightened adapter is installed before the descent between the drill string and the core drill or drill bit. In an emergency, before disconnecting the string, it is stretched by a force exceeding its weight by 5-10%, then first it is rotated to the right with a torque equal to the maximum torque of the drill string joints, then to the left, which leads to its release from the coring shell seized in the well or bits (see tab. 1).

Thus, from this example, on the one hand, it follows that the tensile and torsional compounds proposed otsoedinitelnogo adapter through uniform strength of its component parts is 22% higher than the strength of the drill string connections (Fosn _n> Fosn _k, n. 10, and M _nn > M _pc , p. 18 of Table 1), which excludes the possibility of its breakdown both during drilling and during emergency operations associated with the seizure of a drill. On the other hand, as a result of the elimination of the weak element adapter (non-ferrous metal rings) in the thrust joint and the fulfillment of the condition M _pn > M _pc (item 19 of Table 1), it is ensured that its increased strength and tightness during drilling and reliable disconnection are maintained drill string from a core projectile or drill bit stuck in the well.

Information sources

1. Kopylov V.E., Artyushkin V.N. Quick disconnect and resilient drill pipe joints. - Tyumen: TSU, 1983.P. 96.

2. Reference engineer for exploration drilling: In 2 volumes / Under the general editorship of prof. E.A. Kozlovsky. - Volume I. - M .: Nedra, 1984. 512 p.

3. Lachinyan L.A. Medvedev A.K. Pat. 2549620 RF, IPC E21B 17/042. Threaded connection of drill pipe. No. 20131477559/03. Claim 10/28/2013. Publ. 04/27/2015.

4. Kalinin A.G. and other exploratory drilling. Training for universities. - Nedra - LLC Businesscentre, 2000. - 748 p.

5. Birger I.A. Calculation of threaded connections. Gos. ed. rev. prom M., 1959. 250 p.

6. Lachinyan L.A., Ugarov S.A. Design, calculation and operation of drill exploration pipes and their compounds. M .: Nedra, 1975.232 s.

7. TU 38.101332-90. Grease for threaded connections. Technical conditions

Claims (9)

A disconnecting adapter containing a nipple and a sleeve coupled to each other by a coarse double-thread cylindrical thread, characterized in that the average thread diameter is determined by the expression D _cp = | (D ² + d ² -2h ² ) / 2 | ^0.5 , and the tightening torques of its connection meet the conditions M _pn = M _pc and M _pn > M _pc , Where: D and d are the outer and inner diameters of the adapter; h is the height of the thread profile; M _RP - working torque of the threaded connection of the adapter; M _pc - the ultimate tightening torque of the threaded joints of the drill pipe string (σ _s = σ _t ); M _PP - the ultimate tightening torque of the threaded connection of the adapter (σ _s = σ _t ); σ _s - tension in a dangerous section of a threaded connection; σ _t - yield strength of the material of the threaded connection.

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