Application of High Temperature Cement Slurry Technology in Well Ma Shen 1

The high-temperature and ultra-high-temperature cement slurry technology of Sichuan Hongsheng Petroleum Engineering Technology Service Co., Ltd. has been applied in deep and ultra-deep wells in northeastern Sichuan for a long time. The technology has been continuously improved and the level has been continuously improved. With the current technical level, it can fully undertake the cement slurry technology service required under the ultra-high temperature condition of 180~200 ℃.

In a complete sense, the high temperature and ultra-high temperature cement slurry technology should include two major parts, one is the high temperature and ultra-high temperature cement slurry anti-high temperature admixture drugs, and the other is the high temperature cement slurry formula debugging and performance control. These two major parts of work are the relationship between R & D and application, which are closely linked and mutually promoted, and are equally important and indispensable.

High temperature resistant admixture is the primary factor affecting the performance of deep well high temperature cement slurry. High temperature requires very strict quality of cement admixture. All admixtures must be fully able to withstand the test of high temperature. Cement admixture drugs are required to have stable performance and no deterioration under high temperature conditions, and can normally play their due role to ensure that the performance of high temperature cement slurry meets the design requirements. Since most of the high temperature cement slurry admixture is not a simple molecule, but a multi-polymer, the high temperature admixture plays the role of functional groups. This requires that the polymer functional group can maintain the stability of its structure well under high temperature environment, so as to achieve the stability of its performance. The high-temperature admixture products used in the high-temperature cement slurry technical service project undertaken by Hongsheng Company are all developed and produced by the company itself. Practice has proved that the company's products can fully meet the requirements of high-temperature environment. Due to the influence and restriction of many environmental factors such as material selection, processing technology and so on, coupled with commercial reasons, and the focus of this paper is on the formulation and performance of cement slurry, so the high temperature admixture drugs will not be repeated here.

When it comes to high-temperature cement slurry, people in the industry always have an invisible psychological burden or pressure, which shows that high-temperature cement slurry is very difficult. Temperature is the main factor affecting the performance of cement slurry. The debugging of cement slurry under high-temperature conditions requires a lot of work. Sometimes the debugging workload is very large and it is repeated, but the effect is not ideal. The main reason is that the performance of cement slurry under high-temperature conditions will have some problems that are not easy to control:

(1) Under high temperature conditions, the cement slurry has large water loss, poor settlement stability, low rheological readings, and unstable slurry performance;

(2) Under high temperature conditions, the strength of cement stone develops slowly, and the cement slurry may be super-retarded; the experimental temperature is low, and it may thicken in advance; the high temperature strength of cement stone attenuates obviously;

(3) Under high temperature conditions, the compatibility test of cement slurry is very difficult, sometimes even accounting for 60% of the entire experimental workload;

(4) Under high temperature conditions, the experimental temperature is high, the pressure is high, and the instrument load is too heavy;

(5) ground slurry is difficult, meet the performance of high temperature conditions of cement slurry under low temperature conditions will appear slurry thick, the preparation density can not meet the requirements, uneven density and so on.

There are many reasons for the above problems, coupled with the interaction and correlation between admixture drugs, the solution to the above problems is not one or two experiments and formula adjustment can be effective.

1. high temperature cement slurry technology

1. Water loss control

The original cement slurry has water loss, and the cement slurry without fluid loss reducer cannot control the water loss. High temperature cement slurry must use high temperature resistant fluid loss agent, regular fluid loss agent can not be used for high temperature cement slurry. The performance of regular water loss reducer is greatly affected by high temperature. In high temperature environment, the energy of regular water loss reducer molecules increases, and the kinetic energy of molecules increases accordingly. The mixed structure network formed by linear molecules in cement slurry is easy to be broken, resulting in high temperature dispersion, and more carboxylic acid ions are hydrolyzed, which are adsorbed on (C-S-H) crystals, even the (C-S-H) crystal is completely wrapped, which fully prevents the further reaction of the silicate (C-S-H) gel, prolongs the thickening time and transition time of the cement slurry, and may also appear the phenomenon of super retarding, so the role of the fluid loss reducing agent in maintaining the stability of the slurry is reduced. Therefore, high temperature cement slurry must be used to resist high temperature water loss agent.

The anti-high temperature water loss agent developed by the company is a quaternary polymer containing special functional groups, which is more resistant to temperature than ternary polymers, has strong drug stability, improves the phenomenon of "thermal dilution" at high temperature, avoids secondary crosslinking, and significantly improves the stability of the slurry.

The dosage of fluid loss reducer should be appropriate. If the dosage is small, it will not play the role of reducing water loss. The water loss is too large or even exceeds the design or standard requirements, which does not meet the design requirements. The slurry is thin and the slurry settlement stability is poor, which increases the construction safety risk. The water loss is well controlled, but the cement slurry is very thick, the on-site slurry mixing operation is difficult, the density of the cement slurry cannot reach the requirements, and the density, which seriously affects the cementing quality; the addition amount of water loss reducer should not only ensure the effective control of the water loss of cement slurry, but also take into account the comprehensive performance of the slurry, so it is very important to find the appropriate amount of water loss reducer to adjust the overall performance of the slurry.

Because the spatial network structure formed by the water loss reducer controls the water loss of the cement slurry and also inhibits the hydration rate of the cement. In this sense, the water loss reducer also has some retarder effects.

For technical casing cementing, the water loss requirement of cement slurry is not too high, generally less than 100ml. For gas cementing, the water loss requirement of cement slurry is relatively high, generally less than 50ml.

In addition, latex can also have a fairly good effect on the inhibition of water loss of cement slurry, and the water loss of latex cement slurry can be effectively controlled.

2. Settlement stability

The cement slurry for cementing requires high settlement stability, and the density difference between the upper and lower sides is less than 0.02g/cm3 after standing for 2h. Good settlement stability can ensure that the cement slurry does not produce serious differentiation during the movement and static stages, so as to ensure the stability of the overall performance of the slurry and also help improve the sealing quality of the annular cement ring.

In general, the settlement stability of thick cement slurry is good, the settlement stability of dilute cement slurry is poor, and the settlement stability of high temperature cement slurry is poor.

Rheological properties are related to settlement stability. If the rheological properties are too low, especially if the mantissa of rheological readings is small, the stability of slurry is poor, and the overall performance of cement slurry cannot be guaranteed. If construction is forced, there will be potential safety hazards or even risks.

The high-temperature settling stability of high-temperature cement slurry can be improved by adding high-temperature stabilizers and high-temperature-resistant water loss additives.

Latex also helps to improve the high-temperature settlement stability of high-temperature cement slurry. The latex of latex cement slurry is dispersed in a large amount of dispersed phase in the cement slurry system to disperse the cement slurry, so the latex cement slurry has good settlement stability, and the latex has strong high temperature resistance. Therefore, the performance of latex cement slurry in high temperature environment is stable and good. In addition, the latex system cement slurry can still have a very low consistency (<20Bc) and very good fluidity (constant flow> 20cm) under the condition of good sedimentation stability.

In order to ensure the stability of the latex cement paste under ultra-high temperature conditions, an appropriate amount of latex stabilizer can be added to fully ensure that the latex cement paste under ultra-high temperature conditions with complex ions and high pH value has good sedimentation stability. Can do free liquid volume can be close to "zero", up and down the density difference can be less than 0.01g/cm3.

3. Rheological properties

It is usually required that the fluidity of the cement slurry is good, not only the fluidity at high temperature, but also the fluidity at low temperature can be convenient for construction. Therefore, in the cement slurry experiment, the rheological readings under normal temperature and high temperature conditions should be measured to understand the rheological properties of cement slurry under different temperature environments, and use this as a reference for slurry adjustment.

The rheological properties of cement slurry under high temperature conditions can be improved by optimizing the addition amount of anti-high temperature dispersant. On the premise of meeting the rheological properties in high temperature environment, the addition amount of dispersant is controlled to take into account the rheological properties under normal temperature conditions, so as to ensure the realization of on-site slurry mixing operation. Reasonable fluidity will not increase the burden on the construction pressure, and is beneficial to improve the displacement efficiency of cement slurry and the cementing quality. However, if the rheological properties are too low, especially if the mantissa of the rheological reading is small, the stability of the slurry is poor, and there are potential safety hazards or even risks if the construction is forced. If the viscosity of the mud is large, the cement slurry with too low rheological properties will "point in" during the displacement process, which will seriously affect the displacement efficiency and sealing quality.

The latex in the latex cement slurry has a great influence on the fluidity of the cement slurry. The main reason is that the polymer particles are wrapped into spherical particles by emulsifiers and stably dispersed in the cement slurry. The latex as a dispersed phase is dispersed in a large amount in the cement slurry system to disperse the cement slurry, which has a dispersing and lubricating effect on the cement slurry system. Therefore, the latex cement slurry has good rheological properties, appropriate latex dosage, low viscosity of the cement slurry system, and n value of 0.65~0.95, K value is 0.5~1.40PaSn, good rheology, easy to achieve turbulent flow. However, if the cement slurry is too large, the cement slurry is very viscous, the construction pump pressure is high, the on-site slurry is difficult, and the cement slurry density cannot be increased, which affects the cementing quality.

4. Thickening time

The thickening time is the main performance index of cement slurry, which is related to the safety of construction and the detection of cementing quality. The key to thickening time control is the preference for retarders. The anti-high temperature retarder is preferred to adjust the thickening time of the cement slurry to ensure that the cement slurry has enough pumping time to ensure the safety of construction.

The company's self-developed anti-high temperature drop retarder is a quaternary polymer containing special functional groups, which can fully withstand the test of high temperature and has good stability in drug performance under high temperature conditions.

The retarder compounding method has better stability for the retarding effect of cement slurry, and the specific formula can effectively control the thickening time of cement slurry by compounding AMPS high temperature retarder BS200-G and high temperature retarder BS200R, which provides a basic guarantee for the safety of construction. This conclusion can be confirmed by the divergence experiment of the thickening time of cement slurry after BS200-G and BS200R compound:

Divergence Experiment of Thickening Time of Cement Slurry after Retarder Compound

	160℃×1.90 g/cm3	Density high point 1.93g/cm3	High temperature point 165 ℃
Pin TT,min	562	446	454
Tail slurry TT,min	226	191	187

The experimental results show that there is little difference between the thickening time of the high temperature point and the high density point and the thickening time of the original pulp, which fully shows that the retarding effect is stable, the construction site is assured, and the safety is guaranteed.

There is another characteristic of using this kind of compound retarder, that is, the thickening time of cement slurry has a good linear law with the change of temperature and dosage. This provides a law to follow for the exploration of cement slurry formulations. In addition, this kind of compound cement slurry has good fluidity, normal thickening curve, regular density (1.89g/cm3) cement slurry consistency is lower than 20Bc, generally about 15-20Bc, the transition time is very short, the thickening curve is nearly "right angle", which has advantages in preventing gas-water channeling.

5. Density control

The indoor and on-site control of regular density is relatively simple, while the density control of high-density cement slurry is difficult. Affected by the quality and purity of weighting agent, the density of high-density cement slurry has more influencing factors and is difficult to control. Even if the indoor formula debugging is successful, the on-site preparation may not be realized as desired. High temperature cement slurry due to the addition of high temperature strength stabilizer density is lower than the density of cement, the comprehensive density of cement has some changes, in order to ensure the density of cement slurry, by adding weighting agent adjustment. The addition of these materials must be mixed evenly, especially before the on-site slurry mixing. The uneven dry ash caused by the density difference in the previous intermediate links such as the vibration process during transportation has a great impact on the density uniformity of the slurry mixing. The result is that the thickening time of the part with more cement components is shorter than the experimental value, and the construction is not safe; the thickening time of the part with less cement components is longer than the experimental value, and the super retarding appears.

High temperature and high density cement slurry to add high temperature strength stabilizer, the amount of weighting agent is more, its uniformity requirements are higher. How to overcome the problem of uneven dry ash during long-distance transportation, the effective solution is to blow in from the ash outlet of the vertical tank when filling ash in the vertical tank on site, and use the ash blown in from the back to push up the ash already stored in the tank, so that the uneven dry ash has a chance to be mixed again in the process. This may be inconvenient and adds some pressure to the ash tanker on-site soot blowing, but it is definitely good for the uniformity of dry ash density.

Bubbles may appear in the preparation process of cement slurry, which affects the density of cement slurry. At this time, it is necessary to eliminate the use of efficient foam inhibitors or defoamers.

The density control of ultra-high density cement slurry is more difficult, mainly because the selection and grading of weighting agents need to do a lot of work, and several weighting materials with higher density and purer purity need to be added and matched with reasonable proportions of different particle sizes. Hongsheng Company has continuously summarized and improved the long-term practice of high-density cement slurry in northeast Sichuan. The current technical level is that the density of high-density cement slurry has reached 2.82g/cm3 at the highest level in field application.

6. Strength control

Perforation, fracturing, acidification and long-term mining operations are required for oil and gas wells in the later operation, which requires cement stone to have good strength and toughness. In order to ensure and improve the strength of cement stone, it is generally necessary to add some materials and drugs to improve the strength development and prevent the strength attenuation.

1) Compressive strength of cement stone

Adding the plastic agent BS600 produced by our company can improve the compressive strength and plasticity of cement stone. The plastic agent BS600 contains special fibers, the surface of the fibers is rough, which improves the friction between the fibers and the cement stone. The surface of the fibers is specially treated, with strong affinity, which improves the bonding force with the cement stone. The fibers have good dispersion in the cement slurry and are not easy to agglomerate. Can significantly improve the toughness of cement stone;

Comparison of compressive and flexural data after adding BS600

Type	Density (g/cm3)	Bend strength (MPa)	Compressive strength (MPa)
Paste cement stone	1.90	5.8	25
1% BS600 cement stone	1.90	6.6	32

The destructive test shows that the cement stone still has a certain structure after adding 1% RS600.

It can be seen that the cementing cement stone not only maintains good plasticity, but also has good compressive strength. It can maintain good overall sealing performance under the condition of wellbore pressure change and later drilling operation.

For high temperature cement slurry or large temperature difference cement slurry can add about 1% of the early strength agent TC-2, the early strength of the cement slurry development has obvious effect.

The latex cement slurry system has good plasticity, because the micelle particles of latex are filled between the cement particles, which increases the plasticity of the cement stone, and at the same time can prevent the volume shrinkage of the cement hydration, and because the latex forms a bridge between the cement micro-gaps and inhibits the development of the gaps, the elasticity of the cement stone is enhanced and the impact resistance is improved.

2), cement stone strength decline

The strength of cement paste without measures will decline at high temperature, and the strength of cement paste will decline due to the expansion of calcium silicate generated by sulfate replacement in the formation, which is easy to destroy the structure of cement paste, and the strength of cement paste will decline. The calcium silicate generated by quartz sand can prevent and reduce the formation of calcium sulfate, and the addition of quartz sand can reduce the strength attenuation of cement stone. Experiments show that the addition of micro-silicon and silica fume has a certain effect on ensuring that the cement slurry has high early strength and high temperature strength stability.

There is no clear standard for the addition of quartz sand, and the relevant literature is only for some temperature sections or only a range of addition is given. In order to effectively prevent the strength decline of cement stone under high temperature, through a large number of comparative experiments, through reasonable selection and optimization of silicon calcium ratio, the strength of cement stone under high temperature conditions is more than 14MPa. In order to study the strength decline of cement stone, under the condition that the dosage of quartz sand in the empirical formula is more than 35%, different quartz sand dosage and curing temperature of 200 ℃ are selected to carry out the high temperature strength decline experiment of cement stone. The experimental results are as follows:

Experimental data on strength decline of cement stone with different silica-calcium ratio

Quartz sand dosage	3d	7d	14d	21d	28d
40% quartz sand	17.1	18.5	19.3	20.6	21.2
50% quartz sand	16	17.4	18.4	22.1	24.2
60% quartz sand	13.1	/	/	/	/

Note: The density of cement slurry is 2.20g/cm3.

Through the experiment, it can be seen that the basic strength value of cement stone with 60% quartz sand addition is lower than 14MPa, and the cement stone with 40% and 50% quartz sand addition has no strength decline. Based on the strength attenuation experiment and the original strength data, the quartz sand addition is 40%.

The particle gradation can be considered when adding, and the added quartz sand adopts three different particle sizes of coarse and fine matching, on the one hand, to adjust the rheology of the slurry, on the other hand, to reduce the permeability of cement stone through fine particles (350 mesh) of silica fume.

7. Anti-channeling performance

Most of the high-temperature cement slurry encounters active gas or water layers in deep wells, and the problem of anti-channeling needs to be solved. Therefore, the cement slurry is required to have anti-channeling performance and the anti-channeling coefficient of the cement slurry is required to be less than 3. Generally, the volume of cement slurry shrinks when it solidifies, leaving a channel for gas and water channeling. In order to improve the anti-channeling ability of cement slurry, anti-channeling agent is usually added, which is actually an expansion agent. The anti-channeling agent compensates the chemical shrinkage of cement slurry, increases the volume stability of cement slurry, reduces the channel of gas and water channeling, and plays a role in anti-channeling.

Good cement slurry performance also has the role of anti-channeling, such as: the transition time of cement slurry thickening is very short, the thickening curve is nearly "right angle", the density is uniform, the cement stone permeability is low. From the static gel characteristics, the ring air channeling occurs in the static gel strength 48~240Pa interval, in this interval, the static gel strength development time is shorter, the probability of gas channeling is less. Therefore, the development of static gel strength is fast, strong anti-channeling ability.

In addition, the expansion agent BS500 can expand the cement crystal lattice, which is beneficial to improve the sealing of the interface bonding. It can also improve the anti-channeling ability of cement stone.

To achieve good cement slurry properties, a good cement slurry system must be preferred. Latex cement slurry systems are the preferred system for deep well high temperature cement slurry systems. The latex particles of the latex cement slurry system shall be formed in the cement slurry before cement hydration. These formed particles aggregate under the action of pressure difference to form a latex film that inhibits penetration, which can effectively prevent the formation of free water channels, thus preventing gas or liquid from invading the cement slurry column and preventing gas from escaping upward in the annulus. At the same time, the latex particles of small particles fill the gaps between cement particles and block the channels, reduced permeability, but also effectively prevent gas invasion; more surfactants in the latex, the invasion of gas binding and dispersion. Latex cement slurry has a short transition time, which can completely realize right-angle thickening and right-angle excessive gelation, and effectively prevent formation gas from entering the annulus to destroy the integrity of the cement body. The latex cement slurry can control the lower SPN value, and the anti-gas channeling ability coefficient is less than 3. It has unparalleled advantages over other systems in terms of anti-gas channeling, anti-corrosion fluid, and impact toughness. The excellent performance of latex cement slurry is the best anti-gas channeling cement slurry system to solve high-pressure sulfur gas wells.

8. Pollution resistance

The high temperature mud in deep wells has complex composition and high salinity. In addition, the decomposition and variation of mud drugs in the long-term high temperature environment make the composition in the mud more complex. When the cement slurry contacts and mixes with the mud at high temperature, very complex and various reactions will occur, which will seriously affect the performance of the cement slurry. The phenomenon of contact thickening, thickening time shortening and even coagulation will occur, if it is heavy, the cementing construction fails or cementing construction accidents occur because of early thickening and early solidification.

Ensuring construction safety is a major difficulty and task of high temperature cement slurry. After the preliminary plan of the cement slurry sample experimental formula comes out, the first major event is to continue the pollution experiment. It is best to solve the pollution problem in the cement slurry formula, mainly using retarder, water loss reducing agent and drag reducing agent and other drugs to improve the anti-pollution ability of the cement slurry. The pollution experiment of high-temperature cement slurry cannot be successful after one or two adjustments. It may take a large number of experiments to solve the problem.

The most effective way to improve the anti-pollution ability of cement slurry is to join the company's production of anti-pollution agent KW-2, anti-pollution agent KW-2 on a variety of metal ions, polar functional groups with complexing, chelating and other shielding effect, to avoid cross-linking with the water loss agent, to avoid latex demulsification gel.

Another way to solve the pollution problem is to find a way to increase the amount of retarder in the pre-flush and post-flush systems to improve the anti-pollution ability. If there is still a problem with pollution, the method of increasing the amount of pre-flush liquid and post-flush liquid can be adopted. The increased amount can be considered by increasing at least 20m annular liquid column per 1000m well depth, so that there is no chance and possibility of contact between mud and cement slurry, which is what is usually said to be unaffordable.

Field Application of Well Masen 1 in 2.

Well Ma Shen 1 is an exploratory well. The designed well depth is 8280m and the completed well depth is 8418m, which is the deepest well in China at present. Sichuan Hongsheng Petroleum Engineering Technology Service Co., Ltd. has completed the cementing slurry technology service for the second, third, fourth and fifth wells of the well. Among them, the cementing cement slurry with completion depth of 7699m in the fourth spudh and drilling depth of 8418m in the fifth spudh is a high-temperature cement slurry system. The cement slurry experimental temperature is 135 ℃ and 160 ℃ respectively. The company's high-temperature cement slurry system has been tested again after the successful practice of the cement slurry experimental temperature of 175 ℃ in well Yuanba 3 in 2009. Facts have proved that the company's high temperature cement slurry system is worthy of the name. The well structure is as follows:

Well Blast Structure of Well Mashen 1

Open	Bit size 'well depth mm'm	Cementing method	Casing size 'lower depth mm'm	Sealed well section m
Catheter	914.4'50	single stage	720'50	0-50
open	660.4 '92.73 609.6' 961	single stage	482.6 '959.64	0-959.64
Second opening	444.5 '3 232 406.4 '4297	Positive injection and reverse extrusion	(346.08 339.7)'4292.85	0-4292.85
Three open	311.2 '6225.4	Suspension	273.1 '(4084.59-6203.5)	4084.59-6203.5
		Pin-back	(282.6 273.1 284.2)'4084.59	0～4084.59
Four open	241.3 '7699	Suspension	193 '(5985.79-7699.0)	5985.79-7699.0
		Pin-back	(206.4 193.7)'5985.79	0-5985.79
Five open	165.1 '8418	Suspension	146.1 '(7481.92-8418.0)	7481.92-8418.0

I) Application of Casing Hanging Cementing in 193.7mm Gas Layer of Well Masen 1

The four-way drilling of this well shows 8 layers of good gas layer in 6920.0-7138.90 of Doupo Temple Formation and Longwangmiao Formation. The density of well slurry is 1.95g/cm3, and the static temperature of bottom hole is 160 ℃ after 36h of static time.

1. Test conditions of cement slurry

The temperature is 135 ℃, the pressure is 145MPa, and the heating and boosting time is 60min. Measure the thickening time under constant temperature and pressure.

2. Cement slurry formula:

Lead slurry: Jiahua Grade G Cement + GW-1(40%)+ BS500(3%)+ BS600(1%)+ BS300(1%)+ JZ-II(44%)+ BS100L-G(4%)+ BS200-G(7%)+ JR(12%)+ BP-1A(0.6)

Tail slurry: Jiahua Grade G Cement + GW-1(40%)+ BS500(3%)+ BS600(1%)+ BS300(1%)+ JZ-II(44%)+ BS100L-G(4%)+ BS200-G(5%)+ JR(12%)+ BP-1A(0.6)

3. Cement Slurry Performance

Project	latex collar slurry		latex tail slurry
	Design	Actual	Design	Actual
Density (g/cm3)	2.05	2.05	2.05	2.05
Water loss (ml)	≤50	44	≤50	24
Free liquid (%)	0	0	0	0
72h(167 ℃) compressive strength (MPa)	-	-	≥14	21.2
72h(135 ℃) top compressive strength (MPa)	≥14	18.6	-	-
Initial consistency (Bc)	≤20	20	≤20	19
100Bc thickening time (min)	400-460	438	180-240	225
Density high point (2.08g/cm3) time (min)	360-400	473 (shutdown)	160-220	183
Temperature high point (140 ℃) time (min)	360-400	361	160-220	-
Temperature high point (145 ℃) time (min)	-	-	-	145
Flow degree (cm)	≥ 20	21	≥ 20	21
Sedimentation stability (stationary for 2 hours) Density difference between upper and lower g/cm3	≤ 0.02	0.02	≤ 0.02,	0

4,Rheological data of cement slurry

Name	Φ600	Trillion 300	Φ200	Φ100	Φ6	Φ3
Collar	282	160	116	63	8	6
tail slurry	235	130	94	55	9	6

Pilot slurry	barrier fluid	Flushing fluid	Collar	tail slurry	Mud	Thickening time (min)
10%	10%	20%	60%			420min not thick
25%	25%	25%	25%			400min not thick
10%	20%		70%			400min not thick
33%	33%		33%			400min not thick
				70%	30%	212min thick

6. Site construction

Casing will be started at 23:30 on October 10, 2015, completed at 2:00 on October 12, and then transported by drilling tools. At 19:00 on October 13, drilling tools will transport liner to the bottom of the well (7699) and circulate mud. At 8:00 on October 14, the hanger was successfully disposed of. Cementing is ready at 9:30 on October 14. -14:30 Cementing Construction (Grouting Sequence: 1.95g/cm3 Pilot Grouting 30m3,1.95g/cm3 spacer fluid 15m3,1.02g/cm3 flushing fluid 3m3,2.05g/cm3 collar latex 25m3,2.05g/cm3 tail latex 18m3,1.95g/cm3 plug fluid 2m3,1.95g/cm3 well slurry 33m3, 1.95g/cm3 protection fluid 2.5 m3,1.95g/cm3 of well slurry 56.85 m3,1.95g/cm3 of collision pressure fluid 2.0 m3);-16:00 tripping out 15 columns;-18:00 circulating discharge mixing slurry; -5 columns short at 18:30;-On the 17th, at 16:00, the pressure was suppressed by 12MPa to wait for coagulation.

The whole construction process is safe and smooth, and the cement slurry has good fluidity and uniform density.

7 Effect:

At 21:00 on October 18, 2015, the upper plug surface was drilled to 5722m (the upper plug height was 263.79m).

At 9:00 on October 22, 2015, the lower plug surface was 7605m (the lower plug height was 15.27m).

On October 24, 2015, from 5:00 to 16:00, the sound amplitude was measured electrically (measuring section: 5987-7615m).

The statistics of sound amplitude are as follows:

Length within 15%	900	55.28%	High quality rate	55.28%
15%-30% section length	407	25%	Qualified rate	80.28%
More than 30% section length	321	19.72%	Unqualified rate	19.72%

Logging conclusion: the cementing quality is acceptable.

II) Application of 146.1mm liner suspension cementing in well Mashen-1

The fifth spug drilling of this well shows that good gas layer is encountered in 8108.50-8112.00 of Dengying Group. The well slurry density is 1.43g/cm3, and the static temperature at the bottom of the well is 175 ℃ after 48 hours of static.

1. Test conditions of cement slurry

The temperature is 160 ℃, the pressure is 135MPa, and the heating and boosting time is 90min. Measure the thickening time under constant temperature and pressure.

2. Cement slurry formula:

Lead slurry: JHG +50% sand +1% plastic agent BS600 +2% expansion agent BS500 +1% high temperature stabilizer WD-4 +3% high temperature fluid loss reducer BS100L +12% latex JR +0.7% high temperature retarder BS200-G +4.2% high temperature retarder BS200R +1% drag reduction agent BS300-J +1% stabilizer WD-2 +1% early strength agent TC-2

Tail slurry: HG + 50% sand + 1% plastic agent BS600 + 2% expansion agent BS500 + 1% high temperature stabilizer WD-4 + 3% high temperature water loss reducer BS100L + 12% latex JR +0.7 high temperature retarder BS200-G + 3% high temperature retarder BS200R +1% drag reduction agent BS300-J + 1% stabilizer WD-2 + 1% early strength agent TC-2

3. Cement Slurry Performance

Project	Collar		tail slurry
	Design	Actual	Design	Actual
Density (g/cm3)	1.90	1.90	1.90	1.90
Water loss (ml/6.9MPa × 30min)	≤50	46	≤50	48
72 hours compressive strength (180 ℃× 21MPa)	-	-	≥14	18.9
Top compressive strength at 72 hours (155 ℃× 21MPa)	≥14	16.5	-	-
Initial consistency (Bc)	≤20	16	≤20	12
Thickening time (min)	440-470	562	190-220	226
Density high point (1.93g/cm3) thickening time (min)	400-430	446	160-190	191
High temperature point (165 ℃)	400-430	454	160-190	187
Flow degree (cm)	≥ 20	21	≥ 20	21
Free liquid (%)	0	0	0	0
Settlement stability, density difference between upper and lower 2 hours at rest ≤	0.02	0	0.02	0

Name	Condition	Φ600	Trillion 300	Φ200	Φ100	Φ6	Φ3
Collar	Normal temperature	>300	205	146	85	9	6
	160℃	>300	180	130	75	8	6
tail slurry	Normal temperature	>300	227	152	89	10	8
	160℃	>300	196	135	77	9	6

5Pollution experiment

Cement collar slurry	50%	70%	70%	1/3	/
barrier fluid	50%	20%	10%	1/3	50%
Mud	/	10%	20%	1/3	50%
thickening time	>430min	>430min	>430min	>430min	>430min

6. Site construction.

The liner will be lowered at 0:00 on February 5, 2016, the liner will be lowered at 8:00 on the 7th, and the drilling tools will be lowered. At 4:30 on the 9th, the drilling tools will transport the liner to a well depth of 8414m (without bottoming). Start the pump for circulation, lower the drilling tool to the bottom of the well at 8418m at 10:30, and the hanger is successfully released. -15:15 cementing preparation;-20:30 cementing (construction slurry sequence: 1.43g/cm3 pilot slurry 30 m3,1.55g/cm3 spacer fluid 20 m3,1.02g/cm3 flushing fluid 4 m3,1.88g/cm3 latex lead slurry 11 m3,1.94g/cm3 latex tail slurry 6 m3,1.55g/cm3 plug fluid 2 m3;1.80g/cm3 heavy slurry 7 m3;1.55g/cm3 protection fluid 2 m3,1.43g/cm3 well slurry 58.8 m3, no pressure.); -Short start 15 columns at 22:00;-Cycle at 3:00;-Short start 5 columns at 4:00; -9:00 on February 13, pressure holding 8MPa waiting for coagulation.

The whole construction process is safe and smooth, and the cement slurry has good fluidity and uniform density. On-site operation control is convenient.

7. Construction effect

① At 1:30 on February 15, 2016, drill down to a well depth of 7049.7m to find the cement plug surface, with a plug height of 432.22m.

② On February 20, 2016, at 14:30, drill down to a well depth of 8355m (ball seat position) without plug.

③ Electric logging and cementing quality from 8:00 to 19:00 on February 15, 2016. The sound amplitude of the overlapping section is 20-30%, most of the naked eye section is less than 10%, a small amount is about 10%, and the high quality rate is 93%.

Logging conclusion: the cementing quality is high.