A New Type Cement Slurry System for - PowerPoint Presentation

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A New Type Cement Slurry System for

Deep and High Temperature Wells ZHOU Van-jun1,2 and JIA Jiang-hong2

1.College of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266555, Chnia 2. Institute of Drilling Technology, Shengli Petroleum Administration Bureau, Dongying 257017, China ABSTRACT In deep, high temperature well cement operation, a big difference between the temperatures at both ends of a long cement column existed. Cementing a long interval in one time may cause cement slurry losses into the formations. A low density and high strength cement slurry was developed based on theory of high-packing to solve the problem. Laboratory experiments showed that the formulated cement slurry had advantages of low density, high strength, low fluid loss, excellent rheology and high temperature tolerance, long effect, etc. This formulation has been applied in more than 200 wells and all achieved good results. KEYWORDS: Cementing; fluid, low density cement slurry; long cementing segment; rheology INTRODUCTION With the development of oil field, the proportion of deep well is increasing, long section cementation is taken into use for reducing costs. At present, multi-times cementing is most used in long section cementation of complex well in and abroad [1], however, this needs heavy workload and high costs. Focusing on the problems of over-length cementation, big temperature difference from top and bottom, cement slurry losses and formation pollution causing by high density of cement paste, low density cementation technology research is carried out in and abroad, but Cement strength is generally low, stability is poor and period of validity is short[2]. A high-strength and low-density cement slurry was developed in this paper on the basis of particle grading over numerous experimentation, its property, stability and validity was evaluated. The results show that this system has advantages of low

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1990 density, high strength, low fluid loss, excellent rheology and good stability, high temperature tolerance, corrosion resistant and long effect, it reveals good effects and high economical profits. BASIS AND MECHANICS ANALYSIS OF CEMENTATION SYSTEM DESIGN

The design basis of high-strength and low-density cementation system is high packing theory[3], the slurry system can achieve good gap filling through the choice of active materials and proper distribution of different component size, the filling water and absorbing water was reduced and solid content of unit volume in slurry system was increased, thus the system achieve the effect of close packing. Simultaneously, the system keeps good rheological behavior with the ball effect of micro-filling particle. The silicon particle is as small as 0.15μm, the particle grading can be changed, which reduces the cement porosity and increases the compactness and strength because of specific surface area of silicon, it can absorb large quantities of hydrone, a compact netlike frame was formulated with the particles linking each other, so the cementation has good stability to control hydro loss. Hollow microsphere has a low density(0.7 g/cm3) and a big diameter(150-250μm), which reduce the reliance on water and decrease the water sensibility of silicon particle, decreasing the water-cement ration of cement slurry system, thus, the density of slurry was reduced effectively. The comprehensive performance was increased through adding filtrate reducer, dispersing agent and defoamer. EXPERIMENTAL PART Main experimental apparatus and material Main experimental apparatus: constant velocity stirrer, laid stirrer, constant pressure consistometer, high pressure dehydration meter, NTP rheometer, HPHT consistometer, versatile material testing machines, core flux apparatus, and constant temperature bain-marie. Materials: hollow microsphere, fiber, silicon particle, puffy pearl powder, vermiculite of modified material, CK2, CS of activator, filtrate reducer,langdy-806L,HS-2A,SZ-2,SD15, retarder, PN,SD21,SDPN, cement dispersing agent, langdy-906L, SXY, defoamer, langdy-19L, grade G cement of Jiahua. Experimental process According to the particle size distribution theory of low density slurry, to optimize cementation formulation, admixture such as retarder, dispersing agent, filtrate reducer should be optimized. to test the main function of the cementation system, including thickening time, hydro loss, rheological

behavior, the compression strength of cement. Following the process of API, the test of cementation stability, and compound, maintaining and other functions should be carried out.

EXPERIMENTAL RESULTS AND ANALYSIS Cementation compound and its basic performance To get a better high strength and low density cementation system, numerous of experiments were carried out, optimizing dispersing agent, filtrate reducer, retarder, changing the silicon particle, hollow microsphere, and changing the dosage, then get a different formula, as following: Formula A G Grade Jiahua cement, 25% of hollow microsphere,15% of silicon particle,8.5% of filtrate reducer(langdy-806L), 2.5% of dispersing agent(langdy-906L), 1.2% of retarder(PN), and 0.2% of defoamer(langdy-19L).

Formula B G Grade Jiahua cement, 35% of hollow microsphere, 20% of silicon particle,8.5% of filtrate reducer(langdy-806L), 2.5% of dispersing agent(langdy-906L), 1.2% of retarder(PN), and 0.2% of defoamer(langdy-19L). Formula C G Grade Jiahua cement, 50% of hollow microsphere,30% of silicon particle, 8.5% of filtrate reducer(langdy-806L), 2.5% of dispersing agent(langdy-906L), 1.2% of retarder(PN), and 0.2% of defoamer(langdy-19L). Under the atmosphere pressure in 75℃, the fundamental performance is showed in Table1. Table 1: Conventional properties of the cement slurry formulation density (g/cm3) thickening time (min)

Compressive strength(MPa)- 48h

flexural strength (MPa) - 48h

Water loss (mL)-30 min

A

1.54

431 25.2 2.5 23 B 1.41 448 23.6 1.9 26.2 C 1.29 459 21.1 1.7 28.7

From the Table 1, we can get that system has a fine performance in a whole. In the experimental temperature range, different density of cement has a similar thickening time, which makes the adjustment of formula more convenient, and after 48h time, the strength will get over 20MPa, and API hydro loss will be under 30ml. The rheological behavior of cement paste Increasing the rheological behavior of cement paste can help improve the relevant movement between particles, the stability and substitutability. According to the API standard formula, the rheological parameter can be drawn out, the result was showed in Table2. From table 2 we can get that when the thickness is low, the replacement can get a better efficiency with smoothly replacement.

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1992 Table 2: Rheological parameters of the cement slurry

formulation rheological parameters

¢600

¢300

¢200

¢100

¢6 ¢3 τ0 цP A 179 105 72 36 3 2 4.79 0.07 B 165 95 55 28 3 2

2.87 0.08

C

148

80

50

26 3 2 2.81 0.11

Stability To test the stability of the system, cement paste were injected to a specific steel cylinder under a relatively high temperature of container, got out when ossified, cutting the cement into several pieces and calculating the density. As the Fig.1 saying, the different pieces has a relevant similarity in density, mostly 0.014 g/ cm3, which tell that the cement system has a good stability.

Figure 1: Settlement stability of the cement slurry Temperature tolerance Usually, the temperature tolerance is of the best when the CaO/SiO2 has a mole ratio of 1. Taking the cement of formula B maintaining for 48 hours at different temperatures and testing the strength, the results were showed in Figure 2. From Figure 2, we can get that the system has an increasing strength when the temperature is below 110℃, and decreasing strength when the temperature grows. The whole tendency is smoothing, this is because a certain amount of micro-silicon and floating bead was added in the high-strength low-density cement slurry system, which slowing down the decrease by combing with other particles of cement. So the system has a good temperature tolerance for using in deep well cementation.

Figure 2:

Resistance to high temperatures of the cement slurry Corrosion stability The SiO2 in silicon particle has a low alkalinity, and high activeness, which can react with Ca(OH)

2 of cement and water to get a high resistance of corrosion, and a C-S-H glue with network structure can consume the Ca(OH)2 which corrode the cement mainly. Reducing the big crystal of Ca(OH)2, the corrosion stability is greatly increased. From the Fig.3 we can see that in the high strength low density cement, large amount of hollow microspheres distributed evenly in the cement structure, the particles are enclosed and connected by hydration products. Figure 3: The electron micrographs of cement paste with 1.3g/cm3 Long term validity In order to get the permanent regulation of cement strength, experiments of testing the strength and penetration are taken under normal pressure and 75℃. As formula A, the cement module is 50mm cube block, the strength and penetration is as follows. - 1993 -

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1994 Table 3: Long-term performance of the cement slurry

time Compressive strength (MPa) average compressive strength (MPa) permeability (10-3μm2) average

permeability (10- 3

μ

m

2

)

24h 16.2 15.2 15.9 15.8 0.00042 0.00053 0.00046 0.00047 48h 24.8 26.3 24.1 25.1 0.00036 0.00028 0.00023 0.00029 10d 25.6 27.6 24.4

25.9 0.00032 0.00026

0.00029

0.00029

1mon

28.8

30.3 28.4 29.2 0.00035 0.00023

0.00027 0.00028

2mon 29.2 29.6 29.2 29.3

0.00029

0.00024

0.00026

0.00026

3mon

29.2

30.4

30

29.9 0.00024 0.00023 0.00022 0.00023 4mon 29.2 30.8 32 30.7 0.00024 0.00021 0.00019 0.00021 6mon 28 33.2 32.8 31.3 0.00031 0.00018 0.00021 0.00023 8mon 30.8 32.8 34 32.5 0.00027 0.00023 0.00017 0.00022 10mon 31.6 30.8 33.6 32 0.00023 0.00028 0.00017 0.00023 12mon 29.6 32.8 32.8 31.7 0.00032 0.00025 0.00023 0.00027

From Table 3, the strength is low in 24 hours, but increases quickly from 24th hour to 48th hour, it is increased 9.3MPa, and the compressive strength develops quickly and then slowly, after 12 months, the average compressive strength is still 31.7MPa, the strength is over 25MPa except strength of the 24hours, which can meet the needs of cementing completely. The permeability is less than 0.0003×10-3μm2 except that of the beginning 24 hours, and it shows a good stability of cementation. FIELD USE The system is conducted field test in most oil field based on laboratory tests since 2008, the result shows that this system has a good stability which can be used as an ideal material for cementation in shallow gas well, low pressure and easy leaking well, imbalanced drilling well, deep well, preventing gassed-out well, horizontal well, and direction-fixed well. The system has been widely applied in most oil fields at home and abroad, including Changqing, Turpan-Hami, Tarim, Dagang, Qinghai, Liaohe oil field, which has been used in 200 wells. Among them, the longest cementing section reaches 3400m, the temperature difference from top to bottom reaches 90 degrees and the excellent ratio is over 90%. CONCLUSION The design basis of high-strength and low-density cementation system was achieved based on high packing theory, the whole performance greatly improved, especially the cement strength. The system has advantages of low density, high strength, low fluid loss, excellent rheology and good stability, high temperature tolerance, corrosion resistant and long term validity.

The system can be used as an ideal material for cementation in shallow gas well, low pressure and leaking well, imbalanced drilling well, deep well, preventing gassed-out well, horizontal well, and direction-fixed well, which has good economic profit.

REFERENCES NiuQuanlin, FengNiqian, Yang Jing “Effect of super-fine slag powder on cement properties.” Cement and Concrete Research, 2002, 32 :6 - 15.

Bip in Jain, Schlumberger, Raiturkar A M P, Chris Holmes, Andrew Dahlin. Petroleum Development Oman. Using particle – size distribution technology for designing high-density, high-performance cement Slurries in demanding frontier exploration wells in South Oman. SPE, 59134. Smith M.A. et al. Slag/fly ash cements. World Cement Technology,1997,8:223-233. Paraskevi-Voula Valchou, Jean-Michel Piau. Physicochemical Study of The Hydration Process of An Oil Well Cement Slurry before Setting[J]. Cement and Concrete Research. 1999, 29(1): 27~36. Sabins, F. L., & Sutton, D.L. Interrelationship between critical cement properties and volume changes during cement setting. SPE Drilling Engineering, June 1991:6-8. Roy-Delage, S., Thiercelin, et al. New cement systems for durable zonal isolation. IADC/SPE 59132, 2000:105-107. Morris,W., Criado et al. Design of high toughness cement for effective long lasting well isolations. SPE 81001, 2003:8-9. Low N & Dacoord G. Designing fibered cement slurries for lost circulation applications: case histories. SPE 84617, 2003:15-18. About the Author: ZHOU Yan-jun, doctor, mainly engaged in Oil and Gas Development and Rock Mechanics. e-Mail: jiajianghong79@163.com

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