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Fracturing transformation, as an offensive measure in oil and gas production, has obvious advantages over Other technologies in terms of oil increase. The main battlefield of the exploration and development of Zhongyuan Oilfield - Dongpu Sag is a typical deep and low permeability reservoir. Many oil and gas layers can not achieve the expected development effect without fracturing. In recent years, with the development of objects from one type of reservoir to two or three types of reservoirs, fracturing technology has gradually become the main means of oilfield measures to increase oil.
Fracturing fluid: "blood" is unblocked, "life" is strong
Fracturing fluid is the "blood" of fracturing. It is equivalent to drilling mud and is of great significance for fracturing construction. On the one hand, the fracturing car drives the fracturing fluid into the formation, and the fracturing fluid creates a long slit in the formation to open a passage for oil and gas migration; on the other hand, the proppant is also carried into the formation through the fracturing fluid. It can be said that only the performance of the fracturing fluid is improved, and the fracturing transformation will have a strong "life force".
Since fracturing fluid is a chemical substance that is more or less harmful to the formation, high temperature and low damage are the criteria for measuring the quality of fracturing fluid. At present, the fracturing fluid used in Zhongyuan Oilfield is mainly organic boron fracturing fluid. The fracturing fluid belongs to the category of water-based fracturing fluid, and the main components are tannin extract and organic boron. Its ability to crack and carry proppant is relatively strong. At the same time, it can also adapt to high temperatures below 170 °C. However, since the silicone has a component that is not dissolved in water, the fracturing fluid is also liable to cause some damage to the formation.
In order to minimize this damage, the current approach adopted by Zhongyuan Oilfield is to add some additives to the fracturing fluid to reduce the damage level through the improvement of the fast-discharge process. At the same time, the field is also intensifying research on oil-based fracturing fluids and clean fracturing fluids.
Proppant: "skeleton" is hard, "body" is stable
The fracturing fluid creates a crack in the formation that opens the passage for oil and gas migration. However, under the conditions of formation closure pressure, the fracture may slowly close again, blocking oil and gas migration. How can we avoid this happening? This is the proppant. The proppant enters the formation with the fracturing fluid, stays in the long slit after the fracturing fluid is formed, blocks the crack from closing, and forms a support belt with high conductivity to ensure the successful migration of oil and gas. In this sense, the proppant is quite a "skeleton" of fracturing.
The performance requirements of the proppant can be known from the working principle and environment. Because the proppant needs to stay underground for several kilometers, the temperature resistance is better. At the same time, due to the large closing pressure of the formation, the proppant should have sufficient pressure resistance, the density should be small, and the compactness should be strong. Only then will the proppant not break under the strong formation closure pressure.
Ceramsite sand also has its inevitable shortcomings. Its surface is easy to absorb some dust. These dusts will enter the formation with fluid, which will cause a certain degree of damage to the formation. For this reason, the field is investigating a resin cell coat proppant. This proppant is coated with a layer of resin on the surface of quartz sand for high-pressure, low-permeability well fracturing and to prevent sanding during discharge. The proppant can not only replace the ordinary ceramsite sand, but also control the proppant reflow after hydraulic fracturing. At present, the indoor research of the proppant has been basically completed, and the field application is just around the corner. Fracturing technology: "Comprehensive quality" creates excellent
The fracturing process is the most important part of the entire fracturing process.
At present, there are many more advanced fracturing processes in Zhongyuan Oilfield, such as repeated fracturing, split fracturing, composite fracturing and carbon dioxide foam fracturing.
Repeated fracturing is the fracturing of two or more times in the same well. This is mainly applicable to the fact that a well has a decrease in oil (gas) capacity after prolonged production time after fracturing, or after the fracturing of the well, it has been discovered that other layers have greater development potential after a while, so It is also fractured. Since 1997, Zhongyuan Oilfield has begun to use repeated fracturing on some old wells, with remarkable results. At present, repeated fracturing technology is relatively mature.
Splitting is the selective fracturing of a layer based on geological requirements and oil and gas enrichment systems. Previously, splitting was mainly done by sand filling, sealing or pitching in a layer that was not fractured. This method can only be filled down by pressing or filling, and the transformation of the formation is not complete, and it is difficult to achieve the purpose of splitting. In 2003, Zhongyuan Oilfield achieved the purpose of splitting and splitting through the separator under the non-fracturing layer, and the transformation of the stratum was also thorough. Because the splitting and cracking can completely liberate the second and third class reservoirs, it has been widely used in Zhongyuan Oilfield.
Composite fracturing refers to a mixed fracturing process in which an acidizing process and a fracturing process are used together to put together low, medium and high grade proppants and put together different viscosity fracturing fluids. In this fracturing mode, the performance of the fracturing fluid is particularly critical. The composite fracturing process is mainly applied to the deep and low-permeability reservoirs in the south of the Yellow River in addition to the application in the oil fields in the Yellow River in the East, and the effect is very good.
Since 2003, Zhongyuan Oilfield has promoted the application of carbon dioxide foam fracturing technology. In 2005, this fracturing process was relatively mature in Zhongyuan Oilfield. After being applied in many wells, it has received significant oil-increasing effects.
At present, the fracturing and rebuilding process of Zhongyuan Oilfield has formed a set of supporting technology for fracturing transformation suitable for the development of low permeability oil and gas reservoirs, and has been at the forefront in many aspects in many aspects. However, due to the extremely complicated underground situation and the deepening of the understanding of geology, there are still many problems in the fracturing and transformation process of Zhongyuan Oilfield. First of all, it is still necessary to explore how to solve the damage of deep well fracturing fluid to the formation more effectively. Secondly, in the deep well stratification tool, the oilfield can only fracturing two layers at the same time, which cannot meet the needs of some deep well fracturing. . At the same time, further equipment is needed on the equipment, and a larger-scale fracturing equipment that can adapt to low-permeability and deep-well high-pressure reservoirs is needed. It is believed that these problems will be solved with the further improvement of the fracturing process.
Fracturing technology and technical application of low permeability reservoirs
Fracturing technology is an effective weapon for the development of low permeability reservoirs. But as an offensive measure, it also has some problems.