CN103806855A - Method for determining density of drilling fluid of extremely-thick rock salt stratum - Google Patents

Abstract

The invention relates to a method for determining the density of drilling fluid of an extremely-thick rock salt stratum. The method comprises the following steps that (1) a rock core of a certain depth of an extremely-thick rock salt layer is drilled, creep testing is conducted on the rock core, and a creep deformation parameter A, a creep deformation parameter B and a creep deformation parameter Q of the rock core are calculated; (2) mineral composition testing is conducted on the rock core, and the volume fraction VNaCl of NaCl is measured; (3) several other depths are selected, the step (1) and the step (2) are executed again, the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q of the corresponding depth of the extremely-thick rock salt layer are obtained, and the volume fraction VNaCl of the corresponding NaCl in rock salt is also obtained; (4) in accordance with the data obtained in the step (3), the correlation between the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q and the volume fraction VNaCl of the NaCl is established; (5) the volume fraction VNaCl of the NaCl of the extremely-thick rock salt layer with a continuous change depth is calculated through well logging data; (6) the creep deformation parameter A, the creep deformation parameter B and the creep deformation parameter Q of the extremely-thick rock salt with the continuous change depth are calculated through the established correlation of the A, the B and the C and the VNaCl; (7) the density of the drilling fluid for controlling the well hole shrinkage speed in the full well section of the extremely-thick rock salt stratum is determined, and a drawing plate of the drilling fluid density is drawn.

Description

Definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling

Technical field

The present invention relates to definite method of drilling fluid density in a kind of oil development field, be specifically related to definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling.

Background technology

Along with the continuous exploitation of Shallow Oil-Gas resource, Shallow Oil-Gas resource has approached exhausted, and in order to meet growing energy demand, Deep Oil And Gas Exploration resource and bad ground petroleum resources more and more cause people's concern.Rock salt stratum is the fine cap rock of Hydrocarbon Formation Reservoirs, under rock salt stratum, conventionally containing a large amount of petroleum resourceses, in the Middle East, the area such as Sichuan Basin of the Central Asia, the Gulf of Mexico, China, Tarim Oilfield, Zhongyuan Oil Field, Jianghan Oil-field all found a large amount of petroleum resourceses at subsalt layer.But saline bed is a kind of stratum with extremely strong creeping property, and especially, in the high temperature and high pressure environment of down-hole, rheological characteristic is strong.After well is bored and opened, rock salt well can be along with the continuous undergauge of time, if drilling fluid density is selected improper, bores after opening a period of time and hole shrinkage may occur, caves in, bit freezing, the complex accident such as leakage of thin layer in well.Well creep unique artificial controllable factor in salt cream rock stratum is drilling fluid density, therefore, determines that rational drilling fluid density is of crucial importance in the exploitation of petroleum resources.Creep into by determining that rational drilling fluid density can realize the well creep of salt cream rock stratum to control to ensure safety.

The prerequisite of determining rational drilling fluid density is to obtain the creep parameters on rock salt stratum, traditional method is determining when rational drilling fluid using the creep rate on whole rock salt stratum as a constant, but in actual well drilled, run into a lot of huge thick rock salts stratum, as the Gulf of Mexico of the U.S. has rock salt stratum that several kms are thick as oil gas cap rock, huge thick rock salt stratum is because the degree of depth differs larger, mineral constituent, stress state and the Temperature-pressure Conditions of different layers position rock salt are widely different, and creep parameters also has very large difference.Therefore in the time of huge thick rock salt strata drilling, traditional method is also inapplicable.On the other hand, carry out creep test and can obtain creep parameters although rock salt stratum is drilled through to rock core, when in the face of huge thick rock salt stratum, want to realize that to drill through continuously rock core be that prior art cannot realize.

Summary of the invention

For the problems referred to above, the object of this invention is to provide a kind of definite method of the liquid-tight degree of huge thick rock salt strata drilling with engineering practicability.

For achieving the above object, the present invention is by the following technical solutions: definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling, comprises the following steps:

1) drill through the rock core of a certain degree of depth in huge thick salt rock stratum some, institute's coring is carried out to creep test, and calculate creep parameters A, B and the Q of this rock core; Wherein A, B are rock stream variable element; Q is the activation energy of rock salt;

2) rock core of getting by drilling is carried out to mineralogical composition test, measure the volume fraction V of NaCl in rock salt _naCl;

3) choose other several degree of depth repeating steps 1 of huge thick salt rock stratum) and 2), obtain creep parameters A, B and Q under the respective depth of huge thick salt rock stratum, and the volume fraction V of corresponding NaCl in rock salt _naCl;

4) data that obtain according to step 3), adopt approximating method to set up the volume fraction V of creep parameters A, B, Q and NaCl _naClbetween dependency relation;

5) obtain stratum density ρ, rock salt degree of porosity φ under the continuous varying depth in huge thick salt rock stratum by log data, and the volume fraction V of clay mineral in rock salt _cl, calculate the NaCl volume fraction V under the continuous varying depth in huge thick salt rock stratum by following formula _naCl:

$\mathrm{\φ}\×{\mathrm{\ρ}}_{\mathrm{fluid}}+{\mathrm{\ρ}}_{\mathrm{NaCl}}\×{V_{\mathrm{NaCl}}+V}_{{\mathrm{CaSO}}_4}\×{\mathrm{\ρ}}_{{\mathrm{CaSO}}_4}+V_{\mathrm{cl}}\×{\mathrm{\ρ}}_{\mathrm{cl}}=\mathrm{\ρ}$

$\mathrm{\φ}+V_{\mathrm{NaCl}}+V_{{\mathrm{CaSO}}_4}+V_{\mathrm{cl}}=1$

In formula: φ is rock salt degree of porosity; ρ _fluidfor pore-fluid density; ρ _naClfor NaCl density; V _naClfor the volume fraction of NaCl in rock salt;

for CaSO ₄density;

for CaSO ₄volume fraction in rock salt; V _clfor the volume fraction of clay mineral in rock salt; ρ _clfor clay mineral density; ρ is rock salt density; The wherein density p of each component _fluid, ρ _naCl,

, ρ _clbe given value;

6) A, the B, Q and the V that utilize step 4) to set up _naCldependency relation, calculate creep parameters A, B and Q under the huge thick rock salt continually varying degree of depth;

7) determine that by following formula the full well section in huge thick rock salt stratum is for controlling the drilling fluid density of hole shrinkage speed, and draw drilling fluid density plate:

${\mathrm{\ρ}}_l=100\{{\mathrm{\σ}}_h-\underset{r_w}{\overset{\∞}{\∫}}\frac{2}{\sqrt{3}}\×\frac{1}{B\left(h\right)r}\×1n[\frac{D\left(h\right)r_w^{2}n(2-n)}{2}{\left(\frac{r_w}{r}\right)}^2+\sqrt{{\left(\frac{D\left(h\right)r_w^{2}n(2-n)}{2}\right)}^2{\left(\frac{r_w}{r}\right)}^4}+1\left]\frac{\mathrm{dr}}{H}\right\}$

In formula: D (h) is rock stream variable element; σ _hfor minimally stress of level; r _wfor well radius; R is the distance of stratum apart from borehole axis; H is well depth; N is experience undergauge speed.

In described step 7), the computational methods of hole shrinkage speed n are:

$n=\frac{\mathrm{\ΔS}}{t\·S}$

In formula: Δ S is the variable quantity of well area after creep; T is creep time; S is former well area; And:

$\mathrm{\ΔS}=\mathrm{\π}(R_0^2-R_1^2)$

$S=\mathrm{\π}{R}_0^2$

The computational methods of D in described step 7) (h) are:

$D\left(h\right)=\frac{2}{\sqrt{3}A\left(h\right){{\mathrm{<figure-callout\; id="2"\; label="r\; w"\; filenames="HDA0000464119840000021.png"\; state="\{\{state\}\}">r</figure-callout>}}_w}^2}\exp \left(\frac{Q\left(h\right)}{\mathrm{RT}}\right)$

In formula: h is depth of stratum; R is gas mole constant, i.e. R=1.987cal/molK; T is thermodynamic temperature.

In described step 1), creep test adopts creep of rock testing machine to carry out.

Described step 2) Mineral Component test adopts X diffractometer to carry out.

The present invention is owing to taking above technical scheme, it has the following advantages: the present invention is the new method proposing based on on-the-spot physical condition on the basis that rock salt formation force mathematic(al) parameter laboratory test is measured and on-the-spot log data combines, the method engineering practicability is strong, this can reflect the data of down-hole formation characteristic to take full advantage of log data, through on-site actual situations check, there is good effect.The present invention is applicable to the prediction of huge thick rock salt stratum safe drilling fluid density.

Accompanying drawing explanation

Fig. 1 is flow chart of the present invention;

Fig. 2 is creep test curve and the matched curve under Heard pattern;

Fig. 3 is that huge thick rock salt stratum is for controlling the drilling fluid density plate of hole shrinkage speed.

The specific embodiment

Below in conjunction with drawings and Examples, the present invention is described in detail.

Definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling of the present invention, comprises the following steps (as shown in Figure 1):

1) drill through the rock core of a certain degree of depth in huge thick salt rock stratum some, institute's coring is carried out to creep test, and calculate creep parameters A, B and the Q of this rock core; Wherein A, B are rock stream variable element; Q is the activation energy of rock salt; A, B and Q are all the functions that change with the rock stratum degree of depth.Detailed process is as follows:

Under the Temperature-pressure Conditions of down-hole, the creep of rock salt belongs to the category of dislocation movement by slip, and under the Heard pattern in creep test and down-hole Temperature-pressure Conditions, the creep of rock salt is the most identical.Under Heard pattern, it has been generally acknowledged that the Creep of Salt under higher stress and lower temperature (being less than 250 ℃) is that lattice dislocation slippage is preponderated, Creep of Salt equation so now can be described as:

$\stackrel{\&CenterDot;}{\mathrm{\&epsiv;}}=\mathrm{Aexp}(-Q/\mathrm{RT})\mathrm{sh}\left(\mathrm{B\&sigma;}\right)$

In formula:

for creep rate; R is gas mole constant, R=1.987cal/molK; σ is stress difference; T is thermodynamic temperature.

Getting by drilling after the rock core of a certain degree of depth, can obtain strain-time graph (as shown in Figure 2) by creep test, can obtain creep parameters A, B and Q by the curve under Heard pattern.

Above-mentioned creep test can adopt creep of rock testing machine to carry out.

2) rock core of getting by drilling is carried out to mineralogical composition test, measure the volume fraction V of NaCl in rock salt _naCl.

Above-mentioned mineralogical composition test can adopt X diffractometer to carry out.

3) choose other several degree of depth of huge thick salt rock stratum, repeating step 1) and 2), obtain creep parameters A, B and Q under several degree of depth of huge thick salt rock stratum, and the volume fraction V of corresponding NaCl in rock salt _naCl.

4) data that obtain according to step 3), adopt approximating method to set up the volume fraction V of creep parameters A, B, Q and NaCl _naClbetween dependency relation.

5) obtain stratum density ρ, rock salt degree of porosity φ under the continuous varying depth in huge thick salt rock stratum by log data, and the volume fraction V of clay mineral in rock salt _cl, further calculate the NaCl volume fraction V under the continuous varying depth in huge thick salt rock stratum _naCl.Detailed process is as follows:

Mineralogical composition in rock salt generally comprises NaCl, CaSO ₄, clay mineral (shale) and pore-fluid, between various mineral contents, meet following equation:

$\mathrm{\&phi;}\&times;{\mathrm{\&rho;}}_{\mathrm{fluid}}+{\mathrm{\&rho;}}_{\mathrm{NaCl}}\&times;{V_{\mathrm{NaCl}}+V}_{{\mathrm{CaSO}}_4}\&times;{\mathrm{\&rho;}}_{{\mathrm{CaSO}}_4}+V_{\mathrm{cl}}\&times;{\mathrm{\&rho;}}_{\mathrm{cl}}=\mathrm{\&rho;}$

$\mathrm{\&phi;}+V_{\mathrm{NaCl}}+V_{{\mathrm{CaSO}}_4}+V_{\mathrm{cl}}=1$

In formula: φ is rock salt degree of porosity; ρ _fluidfor pore-fluid density; ρ _naClfor NaCl density; V _naClfor the volume fraction of NaCl in rock salt; for CaSO ₄density;

for CaSO ₄volume fraction in rock salt; V _clfor the volume fraction of clay mineral in rock salt; ρ _clfor clay mineral density; ρ is rock salt density.

The density p of each component in above-mentioned two equations _fluid, ρ _naCl, , ρ _clbe given value.Stratum density ρ, rock salt degree of porosity φ, and the volume fraction V of clay mineral in rock salt _clall can be drawn by log data, therefore, can try to achieve the volume fraction V of NaCl in rock salt by above-mentioned two equations _naCl.

6) A, the B, Q and the V that utilize step 4) to set up _naCldependency relation, calculate creep parameters A, B and Q under the huge thick rock salt continually varying degree of depth.

7) determine that the full well section in huge thick rock salt stratum is for controlling the drilling fluid density of hole shrinkage speed, and draw drilling fluid density plate (as shown in Figure 3), detailed process is as follows:

For controlling the drilling fluid density ρ of rock salt stratum hole shrinkage speed _lcomputational methods be:

${\mathrm{\&rho;}}_l=100\{{\mathrm{\&sigma;}}_h-\underset{r_w}{\overset{\&infin;}{\&Integral;}}\frac{2}{\sqrt{3}}\&times;\frac{1}{B\left(h\right)r}\&times;1n[\frac{D\left(h\right)r_w^{2}n(2-n)}{2}{\left(\frac{r_w}{r}\right)}^2+\sqrt{{\left(\frac{D\left(h\right)r_w^{2}n(2-n)}{2}\right)}^2{\left(\frac{r_w}{r}\right)}^4}+1\left]\frac{\mathrm{dr}}{H}\right\}$

In formula: D (h) is rock stream variable element; σ _hfor minimally stress of level; r _wfor well radius; R is the distance of stratum apart from borehole axis; H is well depth; N is experience undergauge speed.

Wherein, hole shrinkage speed n is defined as:

$n=\frac{\mathrm{\&Delta;S}}{t\&CenterDot;S}$

In formula: △ S is the variable quantity of well area after creep; T is creep time; S is former well area, and:

$\mathrm{\&Delta;S}=\mathrm{\&pi;}(R_0^2-R_1^2)$

$S=\mathrm{\&pi;}{R}_0^2$

In addition, the computational methods of D (h) are:

$D\left(h\right)=\frac{2}{\sqrt{3}A\left(h\right){r_{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="HDA0000464119840000021.png"\; state="\{\{state\}\}">w</figure-callout>}}}^2}\exp \left(\frac{Q\left(h\right)}{\mathrm{RT}}\right)$

In formula: h is depth of stratum.

The drilling fluid density plate obtaining according to said method, can, according to the Creep of Salt situation of full well section, determine rational drilling fluid density.

The present invention only describes with above-described embodiment, and structure, setting position and the connection thereof of each parts all can change to some extent.On the basis of technical solution of the present invention, all improvement of indivedual parts being carried out according to the principle of the invention or equivalents, all should not get rid of outside protection scope of the present invention.

Claims (8)

1. a definite method for the liquid-tight degree of huge thick rock salt strata drilling, comprises the following steps:

1) drill through the rock core of a certain degree of depth in huge thick salt rock stratum some, institute's coring is carried out to creep test, and calculate creep parameters A, B and the Q of this rock core; Wherein A, B are rock stream variable element; Q is the activation energy of rock salt;

2) rock core of getting by drilling is carried out to mineralogical composition test, measure the volume fraction V of NaCl in rock salt _naCl;

3) choose other several degree of depth repeating steps 1 of huge thick salt rock stratum) and 2), obtain creep parameters A, B and Q under the respective depth of huge thick salt rock stratum, and the volume fraction V of corresponding NaCl in rock salt _naCl;

4) data that obtain according to step 3), adopt approximating method to set up the volume fraction V of creep parameters A, B, Q and NaCl _naClbetween dependency relation;

5) obtain stratum density ρ, rock salt degree of porosity φ under the continuous varying depth in huge thick salt rock stratum by log data, and the volume fraction V of clay mineral in rock salt _cl, calculate the NaCl volume fraction V under the continuous varying depth in huge thick salt rock stratum by following formula _naCl:

In formula: φ is rock salt degree of porosity; ρ _fluidfor pore-fluid density; ρ _naClfor NaCl density; V _naClfor the volume fraction of NaCl in rock salt;

for CaSO ₄density;

for CaSO ₄volume fraction in rock salt; V _clfor the volume fraction of clay mineral in rock salt; ρ _clfor clay mineral density; ρ is rock salt density; The wherein density p of each component _fluid, ρ _naCl,

, ρ _clbe given value;

6) A, the B, Q and the V that utilize step 4) to set up _naCldependency relation, calculate creep parameters A, B and Q under the huge thick rock salt continually varying degree of depth;

7) determine that by following formula the full well section in huge thick rock salt stratum is for controlling the drilling fluid density of hole shrinkage speed, and draw drilling fluid density plate:

In formula: D (h) is rock stream variable element; σ _hfor minimally stress of level; r _wfor well radius; R is the distance of stratum apart from borehole axis; H is well depth; N is experience undergauge speed.

2. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 1, is characterized in that, in described step 7), the computational methods of hole shrinkage speed n are:

In formula: Δ S is the variable quantity of well area after creep; T is creep time; S is former well area; And:

。

3. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 1 or 2, is characterized in that, the computational methods of D in described step 7) (h) are:

In formula: h is depth of stratum; R is gas mole constant, i.e. R=1.987cal/molK; T is thermodynamic temperature.

4. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 1 or 2, is characterized in that, in described step 1), creep test adopts creep of rock testing machine to carry out.

5. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 3, is characterized in that, in described step 1), creep test adopts creep of rock testing machine to carry out.

6. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as described in claim 1 or 2 or 5, is characterized in that described step 2) Mineral Component test adopts X diffractometer to carry out.

7. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 3, is characterized in that described step 2) Mineral Component test adopts X diffractometer to carry out.

8. definite method of the liquid-tight degree of a kind of huge thick rock salt strata drilling as claimed in claim 4, is characterized in that described step 2) Mineral Component test adopts X diffractometer to carry out.

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