Fracture fluid plays an important role in the work of hydraulic fracturing, Fracture fluid is good or bad is an important factor related to the success and influence after fracturing construction construction Yield. Since the first successful fracturing technology in field applications, Fracture fluid types used in many construction site, initially based on crude oil, refined oil, oil-based Fracture fluid mainly due later in practice, people gradually realized that the water-based Advantages Fracture fluid, water-based Fracture fluid began to be widely used in construction, are experiencing a few days ago from the main oil-based Fracture fluid gradual transition to water-based Fracture fluid main stage. In recent years, China's vast oil workers and engineering and technical personnel in accordance with Chairman Mao on "independence, self-reliance," the teachings of the cupola of the revolutionary enthusiasm and rigorous scientific attitude combine to make full use of our abundant natural resources, vigorously scientific experiments, various types of fracturing waves have carried out extensive research and testing, preparation plant gum only water-based Fracture fluid used on dozens of experiments, at present, a variety of water-based gel Fracture fluid in field applications have been successful for China's oil industry has contributed to.
In order to make the majority of workers Fracture fluid fracturing have a more comprehensive understanding of, we will introduce the role of Fracture fluid in fracturing construction of Fracture fluid performance requirements, the type of Fracture fluid, the method of preparation, the construction process and how the construction site fracturing According to choose the right Fracture fluid reservoir characteristics.
1.All liquid relations Fracture fluid role in fracturing and stimulation effect of the construction process, the wells (oil) to squeeze into a generic term Fracture fluid.
Fracture fluid is the main role in the construction of the high-pressure ground equipment will be delivered to the formation of an underground reservoir in order to enable the formation of cracks caused by new, distraction or expand existing crack formation, while the proppant to the fracture to go.
Fracture fluid play different roles at different stages of the construction process, called pre-liquid, depending on their role, carrying sand solution for large liquid. In fracturing construction, when the circulation, pressure test, try squeezing processes is completed, the reservoir began to inject high pressure Fracture fluid, which plays a part of the liquid reservoir fracturing the formation of cracks in the role? Called ahead fluid, when the pressure displacement, water absorption index change has been pressure to open the crack to determine, at the beginning of sand, Fracture fluid carrying sand into the cracks, which were part of the liquid is called carrying sand, sand-carrying fluid also plays the role of extension and expansion cracks. Continue Fracture fluid injected into the wellbore sand when completed will bring sand to the wellbore fluid into the cracks of the replacement to avoid sand cards, sand blocking other accidents, often referred to this part of Fracture fluid replacement fluid.
In general, the fracturing pressure to open construction cracks longer, wider, more proppant filled fracture number, the larger the diameter increasing effect of the more significant after fracturing. And to achieve these targets, in addition to the fracturing equipment and other factors, but are directly related to the use of Fracture fluid properties, in general, the amount of fluid loss Fracture fluid is low, will help extend the cracks; Fracture fluid viscosity high pressure in favor of wide open cracks, good performance can be improved suspension Fracture fluid than sand, and can also carry a large diameter sand. Practice shows that the election skewer good performance Fracture fluid fracturing construction can greatly improve efficiency, and can achieve significant yield.
2.Fracture fluid performance requirements
As mentioned above, Fracture fluid is an important factor in determining the success and effectiveness of fracturing of good and bad, so Fracture fluid properties such as fluid loss of several aspects of performance, suspension performance, friction loss, stability and impact on the formation permeability, there certain requirements.
1. Fluid loss performance
Filtrate performance refers to the ability to penetrate Fracture fluid within the formation. We can imagine that in the fracturing construction process, if no fluid loss of liquid using for Fracture fluid, then all of the liquid is injected into the formation of cracks and movement along the extension, so the crack could extend far; but with easy filter lost in the liquid for Fracture fluid formation, the cracks in the process of extending a large number of liquid entering the wall not far from the place where the penetration into the formation to go, it is impossible to extend very deep cracks. For pressure to open and expand the crack, the increase in the consumption of liquid and proppant into the fracture was brought down not far deposition, easy import of cracks caused by sand plug, fluid loss is too high, the pressure may not even crack open. Therefore, the effects of fluid loss performance Fracture fluid for fracturing effect is great. In general, the viscosity of the liquid, the lower the amount of fluid loss, for some liquids, such as fluid loss additive added thereto, the liquid enters the cracks in a thin filter cake can be formed in the rock surface, even Fracture fluid viscosity small, fluid loss is not large. When the construction site, try to use a lower amount of fluid loss Fracture fluid.
2. Suspension Performance
Fracture fluid suspension performance refers Fracture fluid for the proppant (such as quartz sand) in suspending ability. Fracture fluid suspension properties of the proppant may be used in the free settling velocity Fracture fluid expressed. Good suspension properties Fracture fluid and proppant can be all uniformly into the cracks, and to enhance the ratio of sand and proppant carrying larger diameter, the performance difference Fracture fluid suspension, proppant in Fracture fluid will quickly sink, as well as not all sink into the cracks caused by sand poly block, sand cards and other accidents, so that construction can not be carried out smoothly in the wellbore or bottom. Fracture fluid suspension properties are mainly determined by the viscosity of the liquid, specific gravity and velocity in the pipeline or Crack. In general, the liquid viscosity, good suspension performance liquid than the major, strong suspending ability, Fracture fluid velocity in the pipeline or large cracks, strong proppant carrying capacity in the fracturing construction, should try to choose a good performance Fracture fluid suspension .
3. Friction Loss
Fluid flow along the pipeline, due to friction and internal friction between the liquid and the wall between the liquid particles and consume some energy, called the friction loss. fracturing construction, ground equipment, pump pressure, fluid hydrostatic pressure, pipe friction loss and formation fracture pressure between the following:
(Slightly)
As can be seen from the above equation, the local rupture pressure is constant, pipe friction losses Fracture fluid the greater the pressure to open cracks in the ground is not necessary to prepare the higher pump pressure. Friction loss is too large, or even cause fracturing not prepared to act on the bottom of the pressure is less than the fracture pressure, leaving the fracturing failure. Fracture fluid friction loss is small, you can make the ground fracturing fracturing construction were not prepared at low pump pressure of circumstances, will help to extend the life of fracturing equipment. Therefore, the requirements to have the lowest possible Fracture fluid friction losses. In fracturing construction, friction loss and fracturing tuck species size, viscosity, additives and so on. In general, the viscosity of the oil-based Fracture fluid, the greater the friction loss. While smaller friction loss of water-based Fracture fluid. Although water-based gel Fracture fluid generally have a higher apparent viscosity, but in the case of high-speed pump · F difficult to form due to turbulence, friction is not high. Adding certain additives in Fracture fluid in the pipe can reduce friction losses.
4. Impact on the formation permeability
Fracture fluid mechanical impurities and insolubles containing rock blocked pores, or Fracture fluid reacts with the formation of substances causing swelling clay or emulsification, etc., will affect the formation permeability, thus requiring pseudo Fracture fluid mechanical impurities and insoluble content as low as possible, Fracture fluid and the formation of harmful substances should not happen physical and chemical changes, after fracturing easily eliminated from the formation to minimize the impact on the formation Fracture fluid penetration string.
5. Stability
Fracture fluid due to a variety of on-site use, preparation methods, different construction conditions, Fracture fluid may be affected by temperature, air, bacteria and other factors, leaving the performance of some changes, especially when compared with the preparation and construction of the interval long, this problem is more prominent. For example, some water-based glue suspect Fracture fluid viscosity effect by eliminating fine will be reduced, or even spoilage can not cross-linked, so that construction can not be carried out smoothly fracturing. Therefore, the requirements Fracture fluid in the pre-construction and construction process to maintain relative stability. In order to prevent deterioration of the water-based gel Fracture fluid can be added to an appropriate amount of preservative according to the situation. Some Fracture fluid viscosity affected by temperature changes a lot, so when some of the high-temperature wells construction, should choose good viscosity-temperature performance Fracture fluid. In the pre-construction and construction process Fracture fluid properties should be as stable as possible, but you should stick swift solution after Fracture fluid into the formation and easily discharged from the formation.
As can be seen from the above description, an ideal Fracture fluid should have a low fluid loss, good suspension performance, low friction losses, formation permeability damage small and stable performance characteristics. With the rapid development of the oil industry, the scale of construction is increasing fracturing, Fracture fluid amount is large, so the Fracture fluid should also have adequate supply, low cost, easy preparation, etc., in order to meet the needs of large-scale fracturing construction.