CN1814986A - Method for overcomming creep of salt-rock layer by using ralation of drilling fluid density and chloride concentration - Google Patents

Abstract

Present invention refers to a method for overcoming salt rock layer creepage utilizing drilling fluid density and chlorides concentration relationship concentration relationship. It contains 1, to make hole boring with sampling and test sample processing, 2, taking four experiment test samples, to proceed creep test to each test sample, taking multiple level temperature and multiple level loading compound experiment mode to obtain creep test straining and timetable, 3, establishing salt rock creepage constitutive relation equation i.e. creep stress-rate of strain relation equation through curve matching method, 4, establishing well bore necked-in rate and drilling fluid density relation equation,5, taking the rest of four test samples, to proceed salting in experiment, corresponded salting in dissolution rate and chlorides pH indicator relation curve, establishing salting in rate and chlorides pH indicator relational model through nonlinear regression, 6, establishing drilling fluid density, temperature and chlorides pH indicator graph of relation edition, determining rational drilling fluid density and chlorides concentration to overcame salt bed creepage according to steps 6 graph of relation edition to salt bed well drilling in same zone block with experiment well core.

Description

Utilize drilling fluid density and chlorine root concentration relationship to overcome the method for salt bed creep

Technical field

The present invention relates to a kind of method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep.

Background technology

At present in Process of Oil Well Drilling, the salt deposit of bore meeting buries deeply, thickness is big and discontinuous, need the creep of high density drilling fluid control salt deposit, but the salt deposit interval is mingled with low-pressure stratum, the stratum bearing capacity is limited, leakage takes place easily, thereby cause drilling fluid density impossible high, the creep of this wayward salt deposit concerning saturated salt-water drilling fluid.

Creator among the present invention relies on it to be engaged in the experience and the practice of relevant industries for many years for this reason, and through concentrating on studies and developing, finally create a kind of method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep, utilize this method can reasonably adopt chlorine root concentration and unsaturated salt water drilling fluid to come molten creep to separate salt deposit, reduce drilling fluid density and satisfy the minimum burst pressure on stratum, with effective prevention well contract through, prevent the generation of down hole problem.

Summary of the invention

Main purpose of the present invention is to provide a kind of method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep, utilize this method can select suitable drilling fluid density and chlorine root concentration, satisfy the minimum burst pressure on stratum to reduce drilling fluid density, effectively stop well contract through, prevent the generation of down hole problem.

Utilize drilling fluid density and chlorine root concentration relationship to overcome the method for salt bed creep among the present invention, comprise the following steps:

1),, needs several samples of processing altogether to the drilling and coring delivery rock salt rock core sample processing that experimentizes that obtains to seal with wax at the salt rock stratum of a certain construction depth;

2) get in several samples several,, carry out creep test, take the experiment method of multistage temperature and multi-stage loading combination, obtain the strain and the time graph of creep test at the creep of rock testing machine to each sample;

3) by curve-fitting method, set up the constitutive relation equation of rock salt creep, i.e. creep stress-strain rate relation equation;

4) set up the relation equation of well-drilling borehole diameter reducing rate and drilling fluid density;

5) get remaining sample, under different temperatures, carry out the molten experiment of salt, obtain many group salt solute amounts and time relation curve, calculate the corresponding broad relation curve of separating speed and chlorine root concentration of salt, set up the relational model of molten speed of salt and chlorine root concentration by nonlinear regression;

6) set up the plate that concerns of drilling fluid density, temperature and chlorine root concentration;

7) for the salt deposit drilling well of experiment rock core well at same block, can determine that reasonable drilling liquid density and chlorine root concentration are used to overcome the salt deposit creep according to the plate that concerns of step 6).

The method that concerns plate of setting up drilling fluid density, temperature and chlorine root concentration in the described step 6) comprises the following steps:

1) sets up the relational model of molten speed of salt and drilling well diameter reducing rate;

2) set up the relational model of drilling fluid density, temperature and chlorine root concentration;

3) set up the plate that concerns of drilling fluid density, temperature and chlorine root concentration.

Using method in the described step 7) comprises the following steps:

1) degree of depth of estimation salt deposit is calculated the salt deposit temperature according to the stratum temperature gradient;

2) according to the fracture pressure minimum value of salt deposit upper formation, determine drilling fluid density;

3) determine drilling well liquid chlorine root concentration according to drilling fluid density, temperature from concerning plate;

4) adjust drilling fluid density and chlorine root concentration before the salt deposit drilling well, overcome the salt deposit creep and produce hole shrinkage.

The method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep among the present invention mainly is to utilize this method can adopt the unsaturated salt water drilling fluid of suitable chlorine root concentration and density to come molten creep to separate salt deposit, satisfy the minimum burst pressure on stratum thereby reduce drilling fluid density, effectively stop well contract through, prevent the generation of down hole problem.

Description of drawings

Fig. 1 is the strain-time history of No. 1 rock sample among the present invention;

Fig. 2 is the strain-time history of No. 2 rock samples among the present invention;

Fig. 3 is the strain-time history of No. 3 rock samples among the present invention;

Fig. 4 is the strain-time history of No. 4 rock samples among the present invention;

Fig. 5 is 90 ℃ of different salt solute spirograms constantly of the molten experiment of salt;

Fig. 6 is the linear dissolution rate figure of the 90 ℃ of different chlorine root of the molten experiment of salt concentration;

Fig. 7 is 70 ℃ of different salt solute spirograms constantly of the molten experiment of salt;

Fig. 8 is the linear dissolution rate figure of the 70 ℃ of different chlorine root of the molten experiment of salt concentration;

Fig. 9 is 50 ℃ of different salt solute spirograms constantly of the molten experiment of salt;

Figure 10 is the linear dissolution rate figure of the 50 ℃ of different chlorine root of the molten experiment of salt concentration;

Figure 11 is 30 ℃ of different salt solute spirograms constantly of the molten experiment of salt;

Figure 12 is the linear dissolution rate figure of the 30 ℃ of different chlorine root of the molten experiment of salt concentration;

Figure 13 is the graph of a relation of drilling fluid density, temperature and chlorine root concentration.

The specific embodiment

Below in conjunction with accompanying drawing the specific embodiment among the present invention is described in further detail.

The method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep among the present invention mainly comprises the following steps:

1. at a certain construction depth the salt rock stratum of H rice, the rock salt rock core of sealing with wax that drilling and coring delivery the is obtained sample processing that experimentizes, the size standard of sample is that length is 50mm, diameter is the cylinder of 25mm, the quantity of sample is that 8 (also can be other quantity) are individual, and be numbered 1,2 respectively ..., 7,8;

2. get 4 samples (being numbered 1,2,3,4),, on the creep of rock testing machine, carry out creep test, take the experiment method of multistage temperature and multi-stage loading combination, obtain the strain and the time graph of creep test, as shown in Figures 1 to 4 each sample;

The experiment method such as the table 1 of multistage temperature and multi-stage loading combination

Table 1 core experiment mode

Rock sample number	Scheme	Effective confining pressure σ 3	Difference stress σ 1-σ 3	Temperature
					(MPa)	(MPa)	(degree centigrade)
		1	1-1	40				8	60
1-2	12				60
			1-3			16	60
2	2-1				50			8	90
		2-2	12	90
	2-3					16	90
		3	3-1	60				8	120
3-2	12				120
			3-3			16	120
4	4-1				70			8	150
		4-2	12	150
	4-3					16	150

Because the degree of depth that the oil drilling salt deposit occurs mostly is 3000～6000 meters, formation temperature is between 60～150 degrees centigrade, and drilling well liquid columnpressure is general during drillng operation differs 4～20MPa with maximum geostatic stress.It is 3570 meters salt deposit that this experimental sample is taken from the degree of depth, and effective confining pressure and difference stress determines as certificate in the experiment condition.

This experiment is carried out on Terratek rock mechanics test macro, and this system is advanced Programmable Temperature, the control pressurer system of a cover.This system can measure, write down strain continuously and carry out temperature and pressure control automatically according to predefined program schema, because this system is a prior art, therefore structure and the operating principle to system describes in detail no longer separately.

During experiment, the sample sealing is placed in the hyperbaric chamber, is equipped with on the sealing shroud axially and the radial strain sensor, its strain signal arrives data acquistion and control system by data wire.System carries out temperature and pressure control while data acquisition equipment automatically according to predefined program schema and then carry out data sampling in certain time interval, draws strain graph of a relation in time after handling through main control computer, as shown in Figures 1 to 4.

Experimental procedure and method to each sample are as follows:

1) will test rock sample and on experiment frame, place, rock sample axial compression and confined pressure (＜0.1Mpa) fixing rock sample a little;

2) rock sample is heated, and the speed of heating is controlled at per minute 1-2 degree, heats when reaching designated value, adds confined pressure σ ₃, make confined pressure also reach designated value;

3) constant temperature and pressure is about 1 hour, makes the rock sample internal temperature reach even;

4) apply axial load σ ₁Test, keep temperature in the entire test this moment, confined pressure and axially should be constant, and the distortion of noting rock sample is drawn strain one time graph over time.

5) after creep rate tends towards stability, change temperature or stress and carry out creep test under the next stage temperature, pressure condition;

Must be noted that in process of the test the one-level by low stress low temperature begins, do the one-level test of higher temperature or higher stress gradually, between the two-stage test, rock sample is recovered simultaneously as far as possible, to reduce the influence of stress back one-level test.

3. by curve-fitting method, set up the constitutive relation equation of rock salt creep, i.e. creep stress-strain rate relation equation;

Higher and the temperature lower (less than 250 ℃) of oil drilling reservoir stress, the creep of rock salt is generally the dislocation movement by slip of lattice, and this moment, the creep of rock salt can be expressed as follows with exponential equation:

$\stackrel{\·}{\mathrm{\ϵ}}=A\·\exp (-\frac{Q}{\mathrm{RT}})\·\mathrm{sh}\left(\mathrm{B\σ}\right)---\left(1\right)$

In the formula, ε _sSteady state creep speed (1/s); The activation energy of Q rock salt (card/gram molecule); The R ideal gas constant; R=1.987 card/molarity; σ difference stress (Mpa); T absolute temperature (K); A, B rheological constant.

Strain and time graph Fig. 1 to Fig. 4 by test calculate strain rate, see Table 2, by nonlinear regression, can get each parameter of model:

A＝35.275

B＝0.603

Q＝19887

Table 2 creep rate

Rock sample number	Scheme	Strain rate
				1	1-1	2.40969E-10
1-2	2.48357E-09
		1-3	2.49557E-08
2	2-1				2.46111e-09
		2-2	2.58536E-08
	2-3			2.90923E-07
		3	3-1		1.91000E-08
3-2	2.13001E-07
			3-3	2.29160E-06
4	4-1				1.16611E-07
		4-2	1.30601E-06
	4-3			7.43104E-06

4. set up the relation equation of well-drilling borehole diameter reducing rate and drilling fluid density;

Look rock salt stratum geostatic stress for uniformly, it is worth P ₀=σ _H, mud column pressure is P in the well _i, the well radius is a; Suppose that the rock salt stratum is an isotropism, and be plane strain problems; Hydrostatic pressure does not influence the creep of rock salt; The broad sense creep rate

With deviator of stress S _IjHas identical principal direction.Can obtain the mechanics fundamental equation of creep problem according to above-mentioned hypothesis.

Equilibrium equation

$\frac{{\mathrm{d\σ}}_r}{\mathrm{dr}}+\frac{{\mathrm{\σ}}_r-{\mathrm{\σ}}_{\mathrm{\θ}}}{r}=0---\left(2\right)$

Geometric equation

${\mathrm{\ϵ}}_r=\frac{\mathrm{du}}{\mathrm{dr}}$

${\mathrm{\ϵ}}_{\mathrm{\θ}}=\frac{u}{r}---\left(3\right)$

Physical equation

$\stackrel{\·}{{\mathrm{\ϵ}}_0}=\frac{\sqrt{3}}{2}\mathrm{Aexp}(-\frac{Q}{\mathrm{RT}})\mathrm{sh}\left[B^{\′}\frac{\sqrt{3}}{2}({\mathrm{\σ}}_{\mathrm{\θ}}-{\mathrm{\σ}}_r)\right]$

$\stackrel{\·}{{\mathrm{\ϵ}}_r}=-{\mathrm{\ϵ}}_{\mathrm{\θ}}---\left(4\right)$

Fringe conditions

σ _rr＝a＝P _i

σ _rr＝b→∞＝σ _H

(5)

If making the diameter reducing rate of well is n, 1/hrs, determine that then the mechanical model of keeping the required drilling fluid density of given hole shrinkage rate is:

${\mathrm{\ρ}}_l=100\{{\mathrm{\σ}}_H-{\∫}_a^{\∞}\frac{2}{\sqrt{3}}\frac{1}{\mathrm{Br}}\ln [\frac{{\mathrm{Da}}^{2}n(2-n)}{2}{\left(\frac{a}{r}\right)}^2+\sqrt{{\left(\frac{{\mathrm{Da}}^{2}n(2-n)}{2}\right)}^2{\left(\frac{a}{r}\right)}^4+}1\left]\mathrm{dr}\right\}/H---\left(6\right)$

In the formula: r is the distance of stratum apart from borehole axis; σ _HAnd σ _hMaximum geostatic stress of the level that is respectively and the minimum geostatic stress of level; $D=\frac{2}{\sqrt{3}A\·a^2}\exp \left(\frac{Q}{\mathrm{RT}}\right)$

5. get 4 samples (being numbered 5,6,7,8), (normal conditions are 4 different temperatures in different temperatures, occurrence is decided on the degree of depth) under carry out the molten experiment of salt, obtain 4 groups of salt solute amounts and time relation curve, calculate the corresponding broad relation curve of separating speed and chlorine root concentration of salt, set up the relational model of molten speed of salt and chlorine root concentration by nonlinear regression;

Water-base drilling fluid salinity do not reach saturated before, the soluble-salt in the solubilized salt rock stratum (for compound salt deposit, the dissolving NaCl, CaSO ₄Deng), along with the prolongation of dissolution time, salinity increases in the solution in course of dissolution, and rate of dissolution reduces, and according to the experiment of dissolution time and salt solute amount, can set up the relational expression of dissolution time salt solute amount and dissolution time:

w _Dissolving=f (t) (7)

W in the formula _DissolvingQuality for moment t dissolving salt;

The molten speed v of salt _DissolvingCan obtain the time differentiate by following formula:

The contact area of the molten speed of salt and salt block and solution has relation, and under normal conditions, the contact area of salt block and solution is big more, rate of dissolution is got over piece, for this reason, for eliminating salt block and the surface area contacted influence of solution, can adopt the rate of dissolution of salt block per surface area to represent.Can get following formula:

In the formula, v _{The area dissolving}Be the molten speed of the salt on the unit contact area;

A is the contact area of salt block and solution.

Can obtain the salt block density represented with volume divided by salt block density with the rate of dissolution of quality representation to following formula.

In the formula, v _{Linear dissolving}Be the salt block rate of dissolution of representing with volume; ρ _SaltDensity for salt block.

Above unit volume gets final product to such an extent that salt block dissolves thickness after making an appointment than last area, can obtain the dissolving thickness (linear rate of dissolution) of salt block in the unit interval thus.

When salt dissolves, solution C l ^-Corresponding increasing can be measured the Cl on the corresponding time point ^-Content in conjunction with formula 10, can be set up t Cl constantly ^-The relation of content and rate of dissolution, thus Cl set up ^-Content and rate of dissolution concern plate or mathematic(al) representation.

Consider in the experiment that the salt deposit drilling well need adopt KCl DWSW liquid system (KCl dosage generally need about 8%), so select for use KCl salt solution to carry out the molten experiment of salt as solution.

In general, salt rate of dissolution influence factor has: the long-pending and solution viscosity of temperature, salt block and solution contact surface etc.Salt block and solution contact surface amass influences salt block rate of dissolution elimination on the available units contact area.Therefore consider temperature and two kinds of influence factors of solution viscosity in the experiment, consider that the on-the-spot drilling fluid of band solid phase that uses carries out drilling well, Gu viscosity influence adopts actual well drilled liquid to carry out the molten experiment of salt.30 ℃, 50 ℃, 70 ℃, the 90 ℃ molten experiments of salt have been carried out.Obtain 4 groups of salt solute amounts and time relation curve,, calculate the corresponding broad relation curve of separating speed and chlorine root concentration of salt, as Fig. 6, Fig. 8, Figure 10, shown in Figure 12 as Fig. 5, Fig. 7, Fig. 9, shown in Figure 11.

By to above-mentioned data analysis, adopt non-linear regression method, set up the relational model of molten speed of salt and chlorine root concentration, i.e. unit interval unit area salt block rate of dissolution (linear rate of dissolution) v _{Linear dissolving}:

v _{Linear dissolving}=0.0002244[Cl ^-] ²+ 1.9568 * 10 ^-6T ²-4.508 * 10 ⁵[Cl ^-] T

-0.0053119[Cl ^-]+0.00051991T+0.036179

cm/min (11)

In the formula, [Cl ^-] be chlorine root concentration, ten thousand mg/l; T is a temperature, ℃.

6. set up the plate that concerns of drilling fluid density, temperature and chlorine root concentration;

The definition of drilling well diameter reducing rate:

$n=\frac{D_{\mathrm{bit}}-\mathrm{CAL}}{{\mathrm{<figure-callout\; id="1"\; label="D\; bit\; t"\; filenames="A20051000521500142.png,A20051000521500152.png"\; state="\{\{state\}\}">D</figure-callout>}}_{\mathrm{bit}}t}1/h---\left(12\right)$

In the formula, D _BitBe bit diameter, cm; CAL is a hole diameter, cm; The t time, h;

Pour in the radial thickness v of salt deposit in the well in the unit hour _Gush:

v _Gush=nD _BitCm/h (13)

For guaranteeing drilling safety, require to pour in the unit hour the interior salt deposit of well and dissolved away by unsaturated salt water drilling fluid, the molten speed of salt is also drawn with compound salt deposit drilling well diameter reducing rate and should be satisfied:

v _Gush=60v _{Linear dissolving}(14)

Promptly

Promptly

$n=\frac{60}{D_{\mathrm{bit}}}\left\{\begin{array}{c}0.0002244{\left[{\mathrm{Cl}}^{-}\right]}^2+1.9568\&times;{10}^{-6}{T}^2-4.508\&times;{10}^{-5}\left[{\mathrm{Cl}}^{-}\right]T\\ -0.0053119\left[{\mathrm{Cl}}^{-}\right]+0.00051991T+0.036179\end{array}\right\}---\left(16\right)$

And the mechanical model of keeping the required drilling fluid density of given hole shrinkage rate is:

${\mathrm{\&rho;}}_l=100\{{\mathrm{\&sigma;}}_H-{\&Integral;}_a^{\&infin;}\frac{2}{\sqrt{3}}\frac{1}{\mathrm{Br}}\ln [\frac{{\mathrm{Da}}^{2}n(2-n)}{2}{\left(\frac{a}{r}\right)}^2+\sqrt{{\left(\frac{{\mathrm{Da}}^{2}n(2-n)}{2}\right)}^2{\left(\frac{a}{r}\right)}^4+}1\left]\mathrm{dr}\right\}/H---\left(17\right)$

Can obtain the relation of drilling fluid density, temperature and chlorine root concentration according to formula 16 and 17, as shown in figure 13.

7) for the salt deposit drilling well of experiment rock core well at same block, can determine that reasonable drilling liquid density and chlorine root concentration are used to overcome the salt deposit creep according to the plate that concerns of step 6).

Same block well salt layer depth is 4122 meters, and the formation temperature gradient is generally/100 meters of 2.7 degree, and can get the salt deposit temperature is 111.29 ℃;

According to salt deposit top drilling well situation, find that drilling fluid density is greater than 2.17g/cm ³The Shi Fasheng drilling fluid leakage drops to 2.15g/cm ³The time drilling fluid leakage controlled, the drilling fluid density of visible salt deposit drilling well should be controlled at 2.15g/cm ³In, to contract through required drilling fluid density be 2.21～2.30g/cm and control well that the salt deposit creep causes by drilling fluid density fully ³Address this problem, take 2.15g/cm ³Drilling fluid, by adjusting the dissolving of chlorine root concentration since creep pour in salt in the well avoid well contract through.

Definite method of drilling well liquid chlorine root concentration is as follows:

1. at the plate that concerns of drilling fluid density, temperature and chlorine root concentration, as shown in figure 13, find a little 2.15 at axis of ordinates, cross this point and sit straight line YY parallel and transverse axis;

2. cross the straight line XX that line YY arbitrfary point P makes to be parallel to the longitudinal axis, XX hands over curve B and P0 point, and the distance that P point and P0 are ordered is L0, XX friendship curve C and P1, and the distance that P point and P1 are ordered is L1, then the P temperature of ordering is [90+30 * L1/ (L0+L1)] ℃;

3. left and right sides translation XX, the temperature of ordering until P is 111.29 ℃;

4. calculate the value of the intersection point of XX and transverse axis, obtaining chlorine root concentration is 13.2 ten thousand mg/l;

5. before the drillng operation, adjust drilling fluid density to 2.15g/cm ³, chlorine root concentration is 13～140,000 mg/l.

Claims (3)

1. a method of utilizing drilling fluid density and chlorine root concentration relationship to overcome salt bed creep comprises the following steps:

1) at the salt rock stratum of a certain construction depth, the rock salt rock core of sealing with wax that drilling and coring delivery the is obtained sample processing that experimentizes needs several samples altogether;

2) get in several experimental samples several,, carry out creep test, take the experiment method of multistage temperature and multi-stage loading combination, obtain the strain and the time graph of creep test at the creep of rock testing machine to each sample;

3) by curve-fitting method, set up the constitutive relation equation of rock salt creep, i.e. creep stress-strain rate relation equation;

4) set up the relation equation of well-drilling borehole diameter reducing rate and drilling fluid density;

5) get remaining sample, under different temperatures, carry out the molten experiment of salt, obtain many group salt solute amounts and time relation curve, calculate the corresponding broad relation curve of separating speed and chlorine root concentration of salt, set up the relational model of molten speed of salt and chlorine root concentration by nonlinear regression;

6) set up the plate that concerns of drilling fluid density, temperature and chlorine root concentration;

7) for the salt deposit drilling well of experiment rock core well at same block, can determine that reasonable drilling liquid density and chlorine root concentration are used to overcome the salt deposit creep according to the plate that concerns of step 6).

2. overcome the method for salt bed creep according to utilize drilling fluid density and the chlorine root concentration relationship described in the claim 1, it is characterized in that:

The method that concerns plate of setting up drilling fluid density, temperature and chlorine root concentration in the described step 6) comprises the following steps:

1) sets up the relational model of molten speed of salt and drilling well diameter reducing rate;

2) set up the relational model of drilling fluid density, temperature and chlorine root concentration;

3) set up the plate that concerns of drilling fluid density, temperature and chlorine root concentration.

3. overcome the method for salt bed creep according to utilize drilling fluid density and the chlorine root concentration relationship described in the claim 2, it is characterized in that:

Using method in the described step 7) comprises the following steps:

1) degree of depth of estimation salt deposit is calculated the salt deposit temperature according to the stratum temperature gradient;

2) according to the fracture pressure minimum value of salt deposit upper formation, determine drilling fluid density;

3) determine drilling well liquid chlorine root concentration according to drilling fluid density, temperature from concerning plate;

4) adjust drilling fluid density and chlorine root concentration before the salt deposit drilling well, overcome the salt deposit creep and produce also eye undergauge.

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