Well drilling and cementing method for directional straight inclined shaft

Abstract

The invention discloses a well drilling and cementing method for a directional straight inclined shaft. The well drilling and cementing method comprises the steps that reservoir physical properties are obtained according to logging information; presetting a drilling scheme according to reservoir physical properties; drilling an inclined borehole according to the drilling scheme; and well cementation is conducted to obtain the directional straight inclined shaft. According to the well drilling and cementing method for the directional straight inclined shaft, aiming at the difference between the well drilling process of the straight inclined shaft and the well drilling process of a straight well, the physical property of the reservoir is associated with the well drilling scheme, and the well drilling scheme suitable for the reservoir is formed before well drilling, so that the obtained scheme is high in adaptability and effectiveness; the problems that the inclination angle deviation is too large in the drilling process, and the inconformity degree between the actual drilling result and the predicted drilling condition is serious are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling technology, and in particular relates to a drilling and cementing method for directional straight and inclined wells. Background Art

[0002] Well drilling is the process of drilling a cylindrical hole with a certain depth into the formation using mechanical equipment. It is one of the almost necessary processes in the current oil and gas reservoir development process. In the current oil and gas reservoir development process, the drilling holes used for applications such as oil wells and gas wells are usually vertically drilled. Even for horizontal wells, the vertical section is usually drilled first, and then gradually transitioned to the horizontal section through the deflection section to form a horizontal well.

[0003] However, with the continuous development of directional wells and directional wells, in the early 1980s, inclined and vertical well drilling technology appeared in foreign countries and was continuously adopted by some foreign oil fields, but was rarely used in China. In the process of oil and gas reservoir development, it is sometimes necessary to drill inclined wells. For example, if the oil-bearing strata are located under natural barriers such as building areas or rivers, or above the corresponding well position on the ocean, it is impossible or unsuitable to build a drilling platform alone. With the development of oil and gas reservoirs, the demand for drilling technology for straight and inclined wells has become more and more numerous and more and more important.

[0004] Like the drilling of vertical boreholes, the drilling process of straight deviated wells also usually uses rotary drilling to reach the target reservoir. The rotary drilling of the borehole is accomplished by rotating a drill string with a drill pipe and a drill bit at its lower end. Weight is applied to the drill string during rotation to form a borehole in the formation. The drill string is hollow, and as the borehole deepens, drill pipes are added to the drill string to increase its length. However, compared with traditional vertical drilling, during the drilling process, due to the inclination of the wellbore, the force difference on both sides of the drill bit, especially the drill bit, is large, and the drill tool is also affected by buoyancy in the wellbore, resulting in a great difference in the actual drilling pressure from vertical drilling, so the inclination angle of the straight deviated well and the drilling angle may be very different. In addition, due to the inclined drilling, the actual rock formation thickness extended by the drilling is also very different from that of vertical drilling. Therefore, the empirical parameters of vertical drilling are often difficult to apply to the drilling of straight deviated wells in the same reservoir. Summary of the invention

[0005] The purpose of the present invention is to provide a drilling and cementing method for directional straight inclined wells, which solves the technical problems of great difficulty in drilling straight inclined wells and poor control of wellbore angle in the prior art.

[0006] The technical solution adopted by the present invention is: a drilling and cementing method for a directional straight and inclined well, comprising the following steps:

[0007] Step 1: Obtain reservoir physical properties based on well logging data;

[0008] Step 2: Preset the drilling plan according to reservoir physical properties;

[0009] Step 3, drilling the deviated wellbore according to the drilling plan;

[0010] Step 4: Cementing to obtain a directional straight and inclined well.

[0011] The present invention is also characterized in that:

[0012] The reservoir properties in step 1 include reservoir stratification, lithology of each stratification and drilling thickness of each stratification; wherein the lithology of each stratification includes hardness; the drilling thickness of each stratification is determined by the reservoir thickness of the stratification, the inclination angle α of the reservoir and the preset inclination angle β of the wellbore, and is calculated as follows: drilling thickness of each stratification = reservoir thickness of the stratification / cosα / cosβ.

[0013] The drilling plan in step 2 includes drilling tool structure, drilling tool parameters and adjustment plan of drilling parameters, wherein the drilling parameters include drilling time and drilling stop time. The drilling time of each layer is preset according to the drilling thickness, and the drilling stop time between adjacent layers is preset according to the reservoir layer. The drilling tool parameters include drilling pressure and drilling speed. The drilling pressure and drilling speed of each layer are preset according to the hardness of the layer.

[0014] Presetting the drilling pressure and drilling speed of each layer according to the hardness of the layer includes firstly presetting the basic value of drilling pressure and the basic value of drilling speed according to the hardness of the layer; and then calculating the preset value of drilling pressure and the preset value of drilling speed according to the basic value of drilling pressure and the basic value of drilling speed.

[0015] The basic values ​​of drilling pressure and drilling speed are the drilling pressure data and drilling speed data used in the vertical well drilling process for the layer with intermediate hardness in the reservoir.

[0016] The preset value of drilling pressure is calculated by the following formula:

[0017] Preset value of drilling pressure = base value of drilling pressure / (tanβ)2×F / (F buoyancy×cosβ)

[0018] Where, F is the weight of the drill bit, and Fbuoyancy is the buoyancy of the drill bit during the drilling process;

[0019] The preset value of drilling speed is calculated by the following formula:

[0020] The preset value of drilling speed=(base value of drilling pressure / preset value of drilling pressure) 1 / 2×base value of drilling speed.

[0021] Step 3 is specifically as follows: drilling fluid is injected between the drill pipe and the wellbore wall of the wellbore, the drilling fluid circulates downward along the drill pipe and upward along the annulus between the drill pipe and the wellbore wall, wherein the drilling fluid is injected into the wellbore along the lower slope side of the drill pipe close to the wellbore.

[0022] The viscosity of the drilling fluid shall not be higher than 100 mPa·s; the sand carrying speed in clean water shall not be lower than 1.0 m / s.

[0023] Step 4 is specifically as follows: extracting the drill bit and inserting the casing; providing cement slurry containing blast furnace slag and alkali; circulating the cement slurry downward along the casing and upward into the annulus formed between the casing and the wellbore wall; wherein the cement slurry is injected into the wellbore along the lower slope side of the drill pipe away from the wellbore.

[0024] The cement slurry contains clay, and the clay content is not less than 6% and not more than 12% by mass fraction.

[0025] The beneficial effects of the present invention are as follows: the drilling and cementing method for directional straight and inclined wells of the present invention links the reservoir physical properties with the drilling plan in view of the difference between the drilling process of straight and inclined wells and the drilling process of straight wells, and forms a drilling plan suitable for the reservoir before drilling, so that the obtained plan has strong adaptability and high effectiveness, and reduces the problems of excessive deviation of the inclination angle and serious inconsistency between the actual drilling results and the predicted drilling conditions during the drilling process. At the same time, the present invention links the reservoir physical properties with the drilling plan, especially the layered lithology and the drilling plan, adjusts the drilling plan, and makes the formed drilling plan more effective and more applicable, so as to reduce the degree and number of drilling parameter adjustments in the drilling process and improve the drilling efficiency and drilling effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of the drilling and cementing method for directional straight and inclined wells of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] Example 1

[0029] The present invention provides a drilling and cementing method for directional straight and inclined wells, such as Figure 1 As shown, the following steps are included:

[0030] Step 1: Obtain reservoir properties based on logging data, including reservoir stratification, lithology of each stratification and drilling thickness of each stratification; wherein the lithology of each stratification includes hardness; the drilling thickness of each stratification is determined by the reservoir thickness of the stratification, the inclination angle α of the reservoir and the preset inclination angle β of the wellbore, and is calculated as follows: drilling thickness of each stratification = reservoir thickness of the stratification / cosα / cosβ.

[0031] Step 2, preset the drilling plan according to the reservoir physical properties, including the drilling tool structure, drilling tool parameters and the adjustment plan of the drilling parameters; wherein the drilling parameters include the drilling time and the drilling stop time, the drilling time of each layer is preset according to the drilling thickness, and the drilling stop time between adjacent layers is preset according to the reservoir layering; the drilling tool parameters include drilling pressure and drilling speed, and the drilling pressure and drilling speed of each layer are preset according to the hardness of the layer, specifically: firstly, preset the base value of drilling pressure and the base value of drilling speed according to the hardness of the layer, and the base value of drilling pressure and the base value of drilling speed are the drilling pressure data and drilling speed data used in the vertical well drilling process for the layer with the middle hardness in the reservoir; then calculate the preset value of drilling pressure and the preset value of drilling speed according to the base value of drilling pressure and the base value of drilling speed, the drilling pressure is proportional to the hardness of the layer, and the drilling speed is inversely proportional to the hardness of the layer. wherein the preset value of drilling pressure is calculated by the following formula:

[0032] Preset value of drilling pressure = base value of drilling pressure / (tanβ)2×F / (F buoyancy×cosβ)

[0033] Where, F is the weight of the drill bit, and Fbuoyancy is the buoyancy of the drill bit during the drilling process;

[0034] The preset value of drilling speed is calculated by the following formula:

[0035] The preset value of drilling speed=(base value of drilling pressure / preset value of drilling pressure) 1 / 2×base value of drilling speed.

[0036] Step 3: Drill the deviated wellbore according to the drilling plan, specifically: inject drilling fluid between the drilling drill pipe and the wellbore wall, circulate the drilling fluid downward along the drill pipe and circulate upward along the annulus between the drill pipe and the wellbore wall, wherein the drilling fluid is injected into the wellbore along the side of the drill pipe close to the lower slope of the wellbore, thereby reducing the viscosity and filter cake on the side of the lower slope of the wellbore close to the drill pipe, and reducing the pressure on the drill pipe on the lower slope. The viscosity of the drilling fluid is not higher than 100mPa·s; the sand carrying speed in clean water is not lower than 1.0m / s.

[0037] Step 4, cementing, to obtain a directional straight and inclined well, specifically: extract the drill bit and insert the casing; provide cement slurry containing blast furnace slag and alkali; circulate the cement slurry downward along the casing and upward into the annulus formed between the casing and the wellbore wall; wherein, the cement slurry is injected into the wellbore along the side of the drill pipe away from the lower slope of the wellbore, so that the active components in the cement slurry are first solidified on the upper slope. The cement slurry contains clay, and the clay content is not less than 6% and not more than 12% by mass.

[0038] Example 2

[0039] It should be noted that in step 1 of Example 1, reservoir stratification is classified according to the type of rock that forms the rock formation, such as shale rock formation, clay layer, chlorite, mica schist, etc. Lithology refers to the type of rock formation, hardness, porosity, filling material, cracks, etc. of the rock that forms the rock formation. Since the lithology such as porosity, filling material and crack bottom is directly related to the hardness of the rock formation, the present invention directly replaces the lithology of the rock formation with hardness to express the lithology of the rock formation. When acquiring logging data, the data is obtained by measuring the original rock sample.

[0040] The preset inclination angle β of the wellbore refers to the angle between the wellbore and the vertical wellbore, which is lower than 45°. This is because a straight inclined well with an inclination angle higher than 45° is very easy to collapse and block the hole during drilling, and is rarely used. Therefore, the present invention is aimed at a straight inclined well with an inclination angle β lower than 45°. At the same time, in order to further reduce the gap between the lateral displacement of the drilled wellbore and the actual lateral displacement of the wellbore to be obtained, the preset inclination angle β of the wellbore can be lower than the actual inclination angle of the wellbore to be obtained, such as 2 to 3° lower.

[0041] Example 3

[0042] It should be noted that in step 2 of Example 1, since the drilling speed of the drill bit is generally determined, the time required for drilling each layer can be estimated based on the drilling thickness, that is, the preset layer drilling time, and then the drilling parameters of each layer are adjusted based on the preset layer drilling time.

[0043] At the interface of adjacent layers, due to the different lithology of the layers, the reservoir physical properties change dramatically, so it is inevitably accompanied by the adjustment of drilling tool parameters and the process of stress release, and the judgment of drilling conditions. Therefore, when the drill bit enters the interface between the previous layer and the next layer, it is appropriately stopped to facilitate the adjustment of drilling tool parameters, stress release and the judgment of drilling conditions. The residence time can be adjusted according to the degree of lithology difference between the layers, such as the difference in rock hardness. The greater the hardness difference, the longer the residence time. When entering a low-hardness rock layer from a high-hardness rock layer, the residence time is also appropriately extended. For example, when the hardness of the previous rock layer is 6 and the hardness of the next rock layer is 3, the residence time can be 5 to 8 minutes; when the hardness of the bottom of the previous rock layer is 5 and the hardness of the next rock layer is 4, the residence time can be 2 to 3 minutes.

[0044] The buoyancy experienced by the drill bit during the drilling process is an estimated value, which is calculated based on the density of the fluid formed during the drilling process and the volume and density of the drill bit. The calculation method is the same as the calculation method of the buoyancy experienced by a conventional solid in a fluid.

[0045] The structure of the drilling tool can adopt the existing drilling tool structure suitable for inclined and vertical wells. For example, the drill bit can be selected from PDC drill bits, roller drill bits, and full-eye drill bits. It can also use multiple drilling tools in combination. For example, a stable inclination drilling tool with a roller drill bit is used in the surface or shallow strata, a stable inclination drilling tool with a PDC drill bit is used in deep layers with lower rock hardness, and a stable inclination drilling tool with a full-eye drill bit is used in deep layers with higher rock concentration. The diameter of the drill bit, the diameter of the stabilizer, and the diameter of the drill collar can be adjusted according to the diameter of the wellbore to be opened.

[0046] Example 4

[0047] The drilling fluid used in step 3 of Example 1 can be a commercially available drilling fluid, such as a drilling fluid including salt, bentonite, a fluid loss control agent, a stabilizer, carboxymethyl cellulose, barite and other ingredients. Among them, the salt can be a common salt in water such as sodium chloride and magnesium chloride, and the fluid loss control agent can also use a common fluid loss control agent, such as carboxymethyl starch; the stabilizer can be a common stabilizer, such as polyacrylamide. In actual applications, the drilling fluid can also include additives such as lignin sulfonate diluents. The drilling fluid used in the present invention can be purchased on the market, or it can be obtained by purchasing the above-mentioned ingredients and configuring it by itself, so that it meets the above-mentioned viscosity and sand carrying speed required by the drilling fluid.

[0048] Example 5

[0049] The blast furnace slag used in step 4 of Example 1 is a slag with a high glass content, which is usually a hydrous glassy granular material generated by direct contact and rapid cooling of a high-temperature slag melt at 1400°C-1600°C with a large amount of water. Its chemical components mainly include silicon dioxide, aluminum oxide, iron oxide, calcium oxide, magnesium oxide, sodium oxide, potassium oxide, and sulfur. The preferred specific surface area of ​​the present invention is 2000cm 2 / g-15000cm 2 / g, especially 4000cm 2 / g-8500cm 2 The alkali used is usually sodium carbonate, calcium carbonate, sodium hydroxide or sodium bicarbonate, preferably sodium carbonate.

Claims

1. A drilling and cementing method for a directional straight and inclined well, characterized in that: The following steps are involved: Step 1: Obtain reservoir physical properties based on well logging data; Step 2: Preset the drilling plan according to reservoir physical properties; Step 3, drilling the deviated wellbore according to the drilling plan; Step 4: Cementing to obtain a directional straight and inclined well.

2. The drilling and cementing method for directional straight and inclined wells according to claim 1, characterized in that: The reservoir properties in step 1 include reservoir stratification, lithology of each stratification and drilling thickness of each stratification; wherein the lithology of each stratification includes hardness; the drilling thickness of each stratification is determined by the reservoir thickness of the stratification, the inclination angle α of the reservoir and the preset inclination angle β of the wellbore, and is calculated as follows: drilling thickness of each stratification = reservoir thickness of the stratification / cosα / cosβ.

3. The drilling and cementing method for directional straight and inclined wells according to claim 2, characterized in that: The drilling plan in step 2 includes a drilling tool structure, drilling tool parameters, and a drilling parameter adjustment plan, wherein the drilling parameters include drilling time and drilling stop time, the drilling time of each layer is preset according to the drilling thickness, and the drilling stop time between adjacent layers is preset according to the reservoir layer; the drilling tool parameters include drilling pressure and drilling speed, and the drilling pressure and drilling speed of each layer are preset according to the hardness of the layer.

4. The drilling and cementing method for directional straight and inclined wells according to claim 3, characterized in that: The method of presetting the drilling pressure and drilling speed of each layer according to the hardness of the layer includes firstly presetting the base value of drilling pressure and the base value of drilling speed according to the hardness of the layer; and then calculating the preset value of drilling pressure and the preset value of drilling speed according to the base value of drilling pressure and the base value of drilling speed.

5. The drilling and cementing method for directional straight and inclined wells according to claim 4, characterized in that: The base values ​​of drilling pressure and drilling speed are drilling pressure data and drilling speed data used in the vertical well drilling process for the layer with middle hardness in the reservoir.

6. The drilling and cementing method for directional straight and inclined wells according to claim 4, characterized in that: The preset value of the drilling pressure is calculated by the following formula: Preset value of drilling pressure = base value of drilling pressure / (tanβ)2×F / (F buoyancy×cosβ) Where, F is the weight of the drill bit, and Fbuoyancy is the buoyancy of the drill bit during the drilling process; The preset value of drilling speed is calculated by the following formula: The preset value of drilling speed=(base value of drilling pressure / preset value of drilling pressure) 1 / 2×base value of drilling speed.

7. The drilling and cementing method for directional straight and inclined wells according to claim 1, characterized in that: The step 3 is specifically as follows: drilling fluid is injected between the drill pipe used for drilling and the wellbore wall of the wellbore, the drilling fluid circulates downward along the drill pipe and upward along the annulus between the drill pipe and the wellbore wall, wherein the drilling fluid is injected into the wellbore along the lower slope side of the drill pipe close to the wellbore.

8. The drilling and cementing method for directional straight and inclined wells according to claim 7, characterized in that: The viscosity of the drilling fluid is not higher than 100 mPa·s; and the sand carrying speed in clean water is not lower than 1.0 m / s.

9. The drilling and cementing method for directional straight and inclined wells according to claim 1, characterized in that: The step 4 specifically comprises: extracting the drill bit and inserting the casing; providing cement slurry containing blast furnace slag and alkali; circulating the cement slurry downward along the casing and upward into the annulus formed between the casing and the wellbore wall; wherein the cement slurry is injected into the wellbore along the lower slope side of the drill pipe away from the wellbore.

10. The drilling and cementing method for directional straight and inclined wells according to claim 9, characterized in that: The cement slurry contains clay, and the clay content is not less than 6% and not more than 12% by mass fraction.

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