B. R. Wang et al. / Natural Science 5 (2013) 997-1000
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3. DETERMINING THE FORMATE
DRILLING FLUID FORMULATION
3.1. Optimization of Filtrate Reducer
The base slurry: 500 ml Water + 80% Sodium formate.
For the drilling and completion fluid system, filtration
index of effective control system is crucial. We select TJ-
1 for the filtrate reducer. And experiments that addition
amount of TJ-1 is different are conducted. Results are
shown in Table 1.
According to the experimental data in the table, when
addition amount of TJ-1 is 3%, instantaneous water loss
is small, and drilling preliminary requirements can be
satisfied. Combining with the actual use situation, the
TJ-1 that its addition amount is 3% is selected for the
filtrate reducer.
3.2. Optimization of Oil Layer Protective
Agent
In order to further improve the comprehensive ability
of reduction in water loss of system and reduce the
damage of oil and gas layer, we select the optimum oil
layer protective agent in the laboratory. Experimental
results are shown in Table 2.
According to the data in the table, by optimizing, TJ-1
plus JYW-3 can reduce water loss greatly after 150˚C
high temperature hot rolling. So JYW-3 that its addition
amount is 3% is selected for the oil layer protective agent.
3.3. Optimization of Tackifier
Because the viscosity of formate fluid can not meet
needs of drilling fluid viscosity in practical application,
proper tackifier must be added in drilling fluid. We had
carried on the contrast experiment to select tackifier. The
results are shown in Table 3.
Formula 1: The base slurry + 3% TJ-1 + 0.5% TXZ-1
+ 3% JYW-3;
Table 1. Optimization experiment of filtrate reducer.
Formula φ600 φ300 φ6 φ3 Gel pa/pa API ml
The base slurry
+ 1% TJ-1 25 13 00 0/0.5 -
The base slurry
+ 2% TJ-1 32 18 11 0.5/0.5 18 (18)
The base slurry
+ 3% TJ-1 42 24 00 0/0 18 (10)
Table 2. Optimization experiment of oil layer protective agent.
Formula φ600 φ300 φ6 φ3Gel pa/pa YP PaAPI ml
Formula 1 113 64 8 62/2.5 7.5 23.5
Formula 2 187 117 6 42/2.5 23.5 6.5
Formula 3 141 81 3 20.5/1 10.5 2.6
Note: Test conditions of 150˚C, hot rolling for 16 h.
Table 3. Optimization experiment of tackifier.
Formula φ600 φ300 φ6 φ3 Gel pa/paAPI ml
Formula 1 29 15 0 0 0/0 16.5
Formula 2 99 74 17 12 1.5/2.5 8
Formula 3 32 17 0 0 0/0 14
Note: Test conditions of 180˚C, hot rolling for 16 h.
Formula 2: The base slurry + 3% TJ-1 + 0.5% TXZ-2
+ 3% JYW-3;
Formula 3: The base slurry + 3% TJ-1 + 0.5% 80A51
+ 3% JYW-3.
By experimental contrast, we know that TXZ-2 has
good viscosifying action and resistance to high tempera-
ture. So TXZ-2 that its addition amount is 0.5% is se-
lected for the tackifier [2].
Through the above research, finally, the overall for-
mula of the formate clay free drilling and completion
fluid system was determined for: water + 80% sodium
formate + 3% TJ-1 + 0.5% TXZ-2 + 3% JYW-3.
4. PEFORMANCE EVALUATION OF
FORMATE DRILLING FLUID SYSTEM
4.1. Rheological Properties Evaluation
Drilling fluid rheological property is usually described
with rheological curve, plastic viscosity (PV), yield point
(YP), gel strength (Gel), apparent viscosity (AV) and
other rheological parameters of drilling fluid.
According to the experimental data in Ta ble 4, when
the aging temperature is below 150˚C, rheological prop-
erty and building capacity of drilling fluid are stable, the
change is not big. When the aging temperature is higher
than 150˚C, filtration of system increases by much, and
rheological property and building capacity of system
become bad. So temperature resistance capacity of for-
mate drilling fluid system can reach 150˚C.
4.2. Pollution Resistance Experiment
In drilling process, soluble salt and clay which are the
main pollution sources can affect the rheological prop-
erty and filtration property of drilling fluid system. In
view of this, the capacity of soil penetration resistance
and soluble salt pollution resistance of the formate drill-
ing fluid system was evaluated. The results are shown in
Table 5.
According to Ta bl e 5, after formate drilling fluid was
16 h under high temperature 150˚C, in the drilling fluid
system which added soil powder, its plastic viscosity,
yield point and API filtration quantity increased. And
after being polluted with soluble salt, its plastic viscosity
reduced, yield point and API filtration quantity increased.
Changes are within the acceptable range [3].
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