Hydraulic fracturing in Azerbaijan

During long development of many on- and off- shore fields of Azerbaijan highly productive

layers have been considerably worked out and there is an increase observed in the amount of

hardly recoverable oil reserves confined to lower permeable reservoirs, high-viscous oil, water-

oil zones, deposits at late development stage. There are different physical and chemical treatment

methods to be applied in the well bottom zone in order to increase well productivity: hydraulic

and hydro-acid fracturing, pumping of coarse-grained sand into plug-forming wells, acid

treatment, treatment with different (dis-) solvents etc. About 1100-1200 acid treatments of

bottom zone and hydro-acid formation fracturings, more than 1000 hydraulic formation

fracturing and sands pumping, 2000-2500 treatments of bottom zone with HC (dis-) solvents etc.

are held annually.

Formation hydraulic fracturing (FHF) in oil fields of Azerbaijan was used in 1954.

Hydrofracturing is one of mechanical methods to

influence the bottomhole formation zone. Liquid is

being injected under pressure into permeable layer;

under its influence the layer is splitted either by bedding

planes or along natural fractures. To prevent fractures

from closing, coarse sand is being injected together with

liquid; it maintains permeability of these fractures

which by 1000 times exceeds permeability of the intact

rock structure.

Liquids for hydraulic fracturing (sand-carriers)- are

low filterable liquids with non-newtonian properties to

keep liquid in the fracture for a long time. Heavy

Kirmaki oil for a long time was a main liquid for

fracturing and sand carrier in Azerbaijan. According to

the standard measuring device used to determine water

loss of mud, filterability of oil, as mentioned above, his

from 10 up to 130 cm3 per 30 min.

Physical properties of Kirmaki oil

Viscosity by

Kepler, MPa.s

Viscosity by

capillary

viscometer,

MPa.s

Specific gravity

with 30ºC,

gr/cm3

Bound water, % Paraffin, %

198.5 196.6 0.935 - 4.86

Infilling with breakdown agent. In order to decrease the filtration ability of breakdown agent

and fully use hydraulic power of pumping units, chemical agents are used to inject breakdown

agent. However, due to their deficiency they were not used in Azerbaijan. In practice during

formation hydraulic fracturing waste material from oil refinery plant named after K. Karaev

(Baku) is used as a thickener- calcic salt of acid tar, which is obtained while producing oily

additives. Adding such thickener (calcic salt) to Kirmaki oil strongly changes rheophysical

properties and improves formation structure. In order to determine a type of such thickened oil

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(mixture), capillary types were studied using viscometer. The results show that such a mixture is

not subject to Newton's law of motion.

Gravimetric relation of liquid, % Structural

viscosity with

20ºC, centipoise

Stress limit of

shift,

mgr/cm2

Filterability,

cm3 per 30 min oil thickener

100 - 189 56 44

95 5 220 105 5

90 10 248 282 105

85 15 265 510 0

80 20 318 675 0

75 25 360 870 0

70 30 420 1010 0

Efficiency in application of thickened oil. Due to low filterability of thickened oil, amount of

breakdown agent and sand-carrier, and also their pumping rates, were somewhat lower than for

FHF with pure oil. Oil production increase is higher as a result of applied thickened oil compared

to pure oil.

Well

N

Breakdown

agent (oil +

thickener)

Sand-carrier

(oil +

thickener)

Amount

of sand

Oil production increase

with FHF:

original

without use of

thickener

repeated with

use of

thickener

in tons

2307 5+1 20+4 10 without result 1270

2208 5+0,75 30+5 12 1872 175

2190 5+1 28+1 10 498 75

1935 5+1 30+4 10 without result 164

1734 5+0,75 30+4,5 10 without result 548

446 5+0,75 30+4,5 10 without result 56

1984 4+1 20+4 10 without result 100

2364 5+1 30+5 10 without result 385

2138 6+0,75 30+4 10 without result without result

Sand for hydraulic fracturing is quartz sand with grain size of up to 2-3 mm. In practice not

only one but several sandy fractures are used; they are introduced into the fracture successively.

Sand for hydraulic fracturing was delivered to Azerbaijan from Volgograd region. Sand on

the plant in Baku was used for washing, drying, sifting etc. Currently the plant is not

operating.

Rate for liquid pumping. It is known from FHF theory and practice, the higher pump rate - the

higher process efficiency. Actual data shows that injection rate of breakdown agent and sand

mixed with liquid does not exceed 55-60 l/s.

Efficiency of hydraulic fracturing. FHF covered targets with productive series having different

geological and physical properties. FHF efficiency has different values in different targets. Thus

in Lower Kirmaki and Kirmaki Sandy horiozns the efficiency does not exceed 45 %, in the

Maycopian horizons- 55-60 %, and over fields in Azerbaijan - 50 % in total.

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In addition to the number of treatment technological factors, the condition of bottom zone,

properties of fracturing liquid and sand-carrier, well choice etc., FHF is also affected by

physical-chemical characteristics of produced oil. In the wells where oil has high paraffin,

asphaltene and tar content, efficiency from FHF is 42-45 %, and its effect does not exceed 5-7

months. In the wells not producing non-newtonian oil, the effect lasts for13-14 months.

Hydro-acid formation fracturing- is one of mechanical types to impact a layer. It is based on

the ability of hydrochloric acid to dissolve carbonaceous, dolomite and quartz rocks. This

method also facilitates cleaning of filtered well zones, production from which has a considerable

amount of mechanical solids. Once hydro-acid formation fracturing was used in

Muradkhanly field, that has a complicated geological structure with abnormally high

formation pressures and temperature. Main production targets are in the Lower .

Cretaceous horizons. The productive horizons are at 3500-4500 m depth.

Work status as of today. Hydraulic fracturing in Azerbaijan was taken over by the Department

on plugging and increase of oil recovery. As of today, according to the obtained information,

FHF application by State oilcompany of Azerbaijan Republic (SOCAR) declined due to financial

reasons and worn out technical base. There is no information about FHF applied by joint

ventures or operation companies.