CEMENT SLURRY DESIGN

1. CEMENT SLURRY DESIGN LABORATORY Presentation by Amit Nitharwal B.Tech 3 rd year Petroleum engineering University college of engineering, RTU, Kota

2. Cement Manufacturing & Composition Portland cement’s basic raw material: limestone and clay. Oxides of Ca, Al, Fe, Si react at high temperatures in the Kiln (1450– 1500 ⁰C ). When it cools, it becomes balls of cement clinker. After aging in the storage, the seasoned clinker is taken to the grinding mills where gypsum is added to (CaSO 4 .2H 2 O) to retard setting time and increase ultimate strength .

3. composition Cement is thought to be made up of four crystalline components in the clinker that hydrate to form a rigid structure . 1. Tricalcium silicate (3 CaO.SiO 2 or C 3 S) 2. Dicalcium silicate (2 CaO.SiO 2 or C 2 S) 3. Tricalcium Aluminate (3 CaO.Al 2 O 3 or C 3 A) 4. Tetracalcium aluminoferrite (4CaO.Al 2 O 3 .Fe 2 O 3 C 4 AF)

4. Objective of cementing The most important factor in the well completion operation is obtaining a satisfactory primary cementing job. The principle functions of primary cementing are:- 1) To restrict fluid movement between formati0n 2) To support the casing 3) To protect the casing from corrosion 4) Stop the movement of fluid into regular & fractured formations(lost circulation)

5. Successful cementation Good cementation job design. Designer’s knowledge about fluids. Cement additives Procedures to be used in given well condition

6. Cement slurry design parameters Well depth, diameter and casing size. Bottom hole static temperature(BHST) . Bottom hole circulating temperature(BHCT) . Bottom hole pressure(BHP ). Mud density Samples of available cement lot. Cement additives. Water that will be used at the asset.

7. Cement slurry properties Slurry density Thickening time Rheology Fluid loss control Free water content Compressive strength Strength retrogression All these properties should be taken care to maintain well security & integrity

8. Slurry density Density of cement slurry is adjusted to :- Balance the formation pressure Control the loss of slurry in weak zones The effective mud removal. Note : - Normally slurry density is kept higher than mud for facilitating the displacement of drilling mud from annulus. The density difference of .2 to.5 gm/cc is normally recommended b/w mud and cement slurry .

9. Density determined by using mud balance

10. Thickening time Definition :-Thickening time tests are designed to determine the length of time for which a cement slurry remains in a pumpable state under simulated wellbore conditions of temperature and pressure. Total time required to pump the cement slurry into the well bore safely. Normally TT = Job time + 1 hour. Excessive TT causes free water pocket formation & settling of cement

11. HP-HT consistometer High pressure-High temperature consistometer. The pumpability, or consistency, is measured in Bearden Consistency units (BC). HP-HT consistometer

12. RHEOLOGY Flow behavior of fluids under applied stress. Applied force induces flow in liquids. Types Of Flow Laminar Turbulent Plug Slurry is designed for turbulent flow or plug flow. In wells with low annular clearance turbulent flow is desirable for good mud displacement.

13. Rheology of cement slurry govern Mud displacement in the annulus Frictional pressure drop in annulus Hydraulic horse power required to place the cement Note :- By adding (dispersants), the physical properties of fluid are modified in turn controls the flow velocity, pumping rate & pressure losses.

14. fann viscometer The slurry sample should be conditioned for 20 minutes in an atmospheric consistometer before measurements are taken. Readings should be taken at ambient conditions and at BHCT when possible. Readings should also be reported at 200, 100, 60, 30, 6 and 3 rpm.

15. fluid loss control Fluid-loss tests are designed to measure the slurry dehydration during, and immediately after cement placement. The slurry is tested for filtrate loss across a standardized filter press at differential pressures of 1000 psi. Poor F/L control may lead to Loss of water to formations. Change of W/C ratio Increase in slurry viscosity & unpumpability Lost circulation

16. HP-HT filter press The test duration is 30 minutes and results are quoted as ml/30 min ml / 30 min = (ml*84.84) / Sq.root of t in Sec.

17. free water content Quantity of water separates out from slurry in 2 hrs. under static conditions. Permissible limit = 1.4% max. Excessive free water causes: water pockets settling micro channeling % of free water= ml of free water* 1.9 7.6

18. Compressive Strength Strength developed by a cement depends on W/C ratio BHST Time Expressed in Psi Minimum strength to hold casing = 500 psi Low W/C ratio – high strength 35-40% silica is added to prevent strength retrogression.

19. compressive strength testing m/c The slurry samples are cured for 24, 48 and 72 hours at bottom-hole static temperatures and pressures to form cement stone of 2 inch . The above cement stone is then broken in the strength testing m/c. Calculations :- KN* 3.92 = Kg/cm 2 Kg/cm 2 * 14.225 = Psi

20. Strength Retrogression The Compressive Strength of the cement stone above 110 o c Start decreasing and as a result permeability of the cement stone increases. Normally 30-35% Silica flour is added to the cement slurry to combat the Strength retrogression of cement stone. Fine Silica flour addition also reduces Permeability of set cement. At this temp, Silica Combines with Free lime to form durable cementations material and arrests Strength retrogression.

21. Cement additives With the use of additives cement slurry design can be modified according to the well requirements. At present the cement class G can be modified easily through the use of additives . Types of cement additives: Accelerators Retarders Extenders Dispersant Fluid loss additives Anti-gas migration additives Special materials:- Antifoam, silica, suspending, weighting

22. Accelerators Accelerating a slurry means shortening the Thickening Time or reducing the time required to gain Compressive Strength or both. To reduce the thickening time as well as increase the rate of early strength . Used for shallow, low temp. & pressure well. Examples :- 1) NaCl ( 3-10% BWOW ) 2) CaCl2 ( 2-4% BWOC

23. Retarders A material that allows sufficient time for slurry placement by delaying the set of the cement is called a retarder. Retarders delay the hydration of cement to provide sufficient time to pump slurry in the well. Increase thickening time but also delay strength development. Needed when Long pumping times are required. Temperatures are high.

24. Brand Name Manufacturer Effective Temp. Range Property HR-4 Halliburton Up to 76 ºC Solid brown powder -Calcium Lignosulphonate derived from wood. HR-5 Halliburton 52 ºC to 97 ºC Black, solid powder -chemically modified lignosulphonate. HR-12 Halliburton 104ºC to 171ºC Yellowish-brown powder - is a mixture of HR-4 retarder and an organic acid.

25. EXTENDERS Extenders are the additives that reduce slurry density and increase slurry yield. Most allow the addition of extra water to slurry Cement may be lightened to protect the weak formations or slurry yield may be increased to reduce the cost. Examples :- Bentonite, Sodium silicate Pozzolans (Diatomaceous earth, Fly ash, Fume silica

26. Fluid Loss Additives Fluid loss material is added to the cement slurry to help minimize the loss of water from the slurry into the formations. Works by viscosifying the mix water or by plugging the pore throat in the filtrate cake with long polymer chains. Recommended and acceptable filtration loss for various job are:- For casing cementation ----------- 100-200 ml/30min. For liner & squeeze job----------- 50-150mi/30min. For Gas wells ------------------------------50mi/30min.

27. Examples Organic polymers (Cellulose) Poly( ethyleneimine ) Polyallylamine Halad-9 (15.5 ºC to 149ºC) Halad-413 (Up to 204º C)

28. DISPERSANTS Dispersants are also called friction reducers, these materials make cement slurries easier to mix and pump. Also called friction reducers, these materials make cement slurries easier to mix and pump by making them less viscous. Act on surface charges of the cement grains. Polyanions- polymelamine, polynapthalene, polystyrene sulpfonates Examples :- CFR-3

29. Anti gas migration additives Gas migration control additives are used to reduce the risk of gas invading the cement and migrating into the wellbore. Examples :- 1) BA-10S 2) BA-10L

30. Heavy weighting additives Weighting material are cement additives that are capable of increasing the density of the cement slurry. These are required to counter high formation pressures. Common high density materials are:- Hematite Barite (Barite is a barium sulfate material used to weight drilling mud and cement slurries)  

31. Thanks for your attention