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Fracturing Additives

Brief Introduction of DDF System of Super Molecule Surfactant Clean Fracturing Fluid

I. Introduction
Super molecule surfactant clean fracturing fluid is a new kind of clean fracturing fluid system developed by our company based on the design theory of new polymer molecular structure. The product meets with the requirements of General Technical Specification of Fracturing Fluid, SY/T6376-2008.

2. Brief Introduction of Product
The DDF system may make use of convertible multi-association among relative powerful molecular chains in dilute solution to form super molecule aggregate, which has similar special network structure to cross linked polymer, so the DDF system will have all the characteristics of clean fracturing fluid without cross-linking.
DDF system of super molecular surfactant clean fracturing fluid includes:


No.

Name

Types & Specifications

Remarks

Normal System

1

Thickener

DDF-1

 

2

Assist thickener

DDF-2

 

3

Assist gel breaker in low temperature

DDF-3

 

4

Gel breaker (ammonium persulfate)

NH4S2O8

 

High Temperature System, above 90℃

1

Thickener

DDF-1H

 

2

Assist thickener

DDF-2H

 

3

Stabilizer in high temperature

DDF-3H

Formation temperature>110℃

4

Gel breaker(capsule)

NH4S2O8
(capsule)

 

III. Product Features
1. Clean and Low Damage
Totally dissolved in water, there is no precipitation and floccule during the whole process. There is no insoluble matter after gel breaking and any damage or low damage to reservoir. It is the ideal clean fracturing fluid system.
2. High Efficiency Viscosifying Ability
In very low concentration (0.4%) circumstance, super molecular surfactant clean fracturing fluid thickener DDF-1 has higher viscosity, combined with assist thickener DDF-2, the viscosity and structure of dilute solution will be greatly enhanced, thus show extremely good high efficiency viscosification ability.
3. Super-strong Suspension
The dilute solution of super molecule surfactant clean fracturing fluid has relatively high association structure and shows excellent viscoelastic and dilution shearing behavior. It will show good suspension without cross-linking, combined with DDF-2, the structure will be obviously improved, and DDF-1 will show super-strong suspension to the proppant when the viscosity is only around 40mPa.s.
4. Super-wide range of Temperature Adaptability: 30 ~ 160℃
Usually, it is difficulty to apply clean fracturing fluid system in both extremely low and high temperature zone, but DDF system solves the above problems very well and shows super-wide range of temperature adaptability.
Super-low Temperature Zone: 30 ~ 50℃, low DDF-1 concentration (0.3 ~ 0.4%), good rheological property, no cross-linking, combined with low temperature assist gel breaker DDF-3, DDF-1 may totally break gel and flowback extensively, therefore, solve the traditional problem of gel breaking in low temperature.
Super-high Temperature Zone: 120 ~ 160℃, the stabilization technology of polymer in high temperature also shows excellent behavior of super molecule surfactant clean fracturing fluid.
5. Good Salt-resistance Behavior
Oligopolymerization system has excellent salt-resistance behavior, super molecule surfactant clean fracturing fluid system may be applied in saline system, such as KCl, even can be made by sea water and produced backwater. Therefore, fracturing work can be implemented both in drilling platform and arid area. In weak acidity (e.g. CO2 foam system) or alkali conditions, compatibility is also good.
6. Excellent Shear Stability, Little Friction
There is no cross-linking in DDF clean fracturing fluid system, so the solution has convertible structure with extremely well shear stability and is easy for transmission of pressure, thus, little friction. Rheological property will not be obviously damaged through the process of pump delivery, perforation and infiltrating.
7. Low Cost
Among clean fracturing fluid, the amount of DDF oligopolymerization system is one of the least consumptions. Concentration may reach 0.4%, but for the traditional VES clean fracturing fluid system, the concentration may be 10 times than that of DDF, and so the cost is low.

IV. Technical Description


Type

Items

Description

Middle ~ Low Temperature

DDF-1

Apparent

White or slight yellow
powder solid

Water Content, %                

≤10

Residue Amount (50 mesh), %      

≤10.0

(25 ± 3℃), Apparent Viscosity of Base Fluid 
0.5%, mPa•s              

≥40

Swelling Time, min            

≤25

Dynamic Viscosity after Gel Breaking (90℃,4h), mPa·s

≤5

Ability of Temperature-resistance and Shearing-resistance (90℃, 60min), mPa·s

≥60

DDF-2

Apparent

Colorless or light yellow liquid

pH Value

>7.0

Escalating Rate of Viscosity, %           

≥15.0

DDF-3

Apparent

Colorless or light yellow liquid

Density (20℃±5℃), g/cm³ 

0.950~1.150

Assist Low Temperature Gel Breaking Dynamic Viscosity (45℃, 12h),  mPa·s

≤5

High Temperature

DDF-1H

Apparent

White or slight yellow
powder solid

Water Content, %                

≤10

Residue Amount (60 Mesh), %      

≤10.0

Viscosity of Water Solution, mPa•s        

≥25

Swelling Time, min            

≤10

DDF-2H

Density (20℃±5℃), g/cm³  

1.00~1.10

Surface Tension, mN/m          

≤35

RI, nD

1.300~1.400

Escalating Rate of Viscosity, %            

≥15.0

DDF-3H

Apparent

Colorless or milky liquid

pH Value

3.0~7.0

Density (20℃±5℃), g/cm³  

1.00~1.20

Increase Rate of Viscosity, mPa•s        

≥10

V. Madeup Proportition (Recommended)
1. Madeup Proportition


No.

Temperature Range

Madeup Proportition

1

30 ~ 40℃

0.35%DDF-1 + 0.20%DDF-2+ 0.2%DDF-3  + 0.2% ammonium persulfate

2

50 ~ 60℃

0.40%DDF-1 + 0.25%DDF-2  + 0.05% ammonium persulfate

3

70 ~ 80℃

0.50%DDF-1 + 0.35%DDF-2+0.5%KCL  + 0.03% ammonium persulfate

4

90 ~ 100℃

0.60%DDF-1H + 0.30%DDF-2H+1%KCL  + 0.03% encapsulated gel breaker

5

110 ~ 120℃

0.70%DDF-1H + 0.40%DDF-2H +1%KCL + 0.02% encapsulated gel breaker

6

130 ~ 140℃

0.75% DDF-1H + 0.5%DDF-2H + 0.2%DDF-3H+1%KCL  + 0.02% encapsulated gel breaker

2. Madeup Procedure
First:
Measure 800ml water with dosimeter and pour it into 1000 ml beaker, switch on agitator (Note: rotary speed ≤600 r/m) till vortex forms, add thickener DDF-1 and DDF-1H, already weighted, into beaker slowly, then fully agitate for 15 ~ 20 min, till sufficient swelling of the primary solvent. Base fluid is compounded.
Second:
Calculate the dosage of rheological assist agent DDF-2 and DDF-2H according to formula and temperature range, extract thickener with liquid changing tube and add it into base fluid, after 1 ~ 2 min agitation, super molecule surfactant clean fracturing fluid is made up.
Enclosing: if there is any more additive (e.g. KCl, high temperature stabilizer DDF-3H, low temperature assist gel breaker DDF-3H and etc.), add them in succession.
Note: 1) Due to the anti-swelling effect of DDF, so the proportion of KCl should be less than 1%.
2) If there is any more addictive, such as clay stabilizer, compatibility test must be needed.

VI. Performance Evaluation
(1) Rheological Test: use rheometer to test the rheological behavior of the already madup super molecule surfactant clean fracturing fluid, test temperature is the actural formation temperature, test time is usually 30 ~ 120 min; shearing rate of rheometer is 170 s-1.
(2) Gel Breaking Test: weight 200g already compounded uper molecule surfactant clean fracturing fluid and then add gel breaker, ammonium persulfate or potassium persulfate, place it in water bath (Temperature: formation temperature, when the formation temperature is more than 90℃, water bath temperature need to be measured at 90℃) . Measure viscosity with 6-speed rotary viscometer every 30 min, the time when the system viscosity is less than 5mPa.S is gel breaking time.
(3) Based on SY/T 5107-2005 Recommended practices on measuring the properties of water-based fracturing fluid to conduct measurement of other behaviors of fracturing fluid, national and company standard in consumer locality is also available.

VII. Compound Methods of Gel Breaker
1. Below 45


No.

Temperature Range

NH4S2O8(Concentration %)

DDF-3(Concentration %)

1

20 ~ 45℃

0.3

0.3

2. Above 45
After adding gel breaker into clean fracturing fluid, heat to assigned temperature in ambient atmosphere, the result is following:
The heating time of super molecule surfactant clean fracturing fluid to assigned temperature is about 20 ~ 30 min, if the formation temperature is more than 100℃, measure it as 90℃.


No.

Temperature
(℃)

DDF-1 (Concentration %)

DDF-2 (Concentration %)

NH4S2O8 ammonium persulfate(Concentration %)

Gel Breaking Time
(min)

1

50

0.35

0.2

0.1

240

2

60

0.45

0.3

0.05

240

3

70

0.5

0.3

0.05

120

4

80

0.55

0.35

0.01

90

5

90 and above

0.6

0.4

0.005

90

VIII. Package and Storage
Three-in-one braided bag, 25kg/bag, or according to customers’ requirements. The product is affected with damp, need to store in cool and dry house. Use sealed package to prevent damage and sun and rain in the transportation.

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