Research And Application Of Surfactant Acidic Fracturing Fluid

Boron cross-linked hydroxylpropyl guar has being the dominant fracturing fluid for several decades although various low-residue fracturing fluids have been developed in recent years. The difficulties of the damage disposal of water-based fracturing liquid include the paths of filtration of reservoir liquid are blocked up by macromolecule matter and backup cracks are blocked up by dreg of fracturing liquid. Research on the difficulties has been performed. But they aren't sloved well.In the dissertation,fracturing fluid of free damage has been studied in order to avoid the difficulties above the fracturing fluid haven't macromolecule and dreg in gel breaker. Filter liquor is acidity which can improve the formation permeability.The damages of particle motion and the falling off of clay mineral in fractures can be avoided. The damage of filter cake to fracture surfaces and the congestion damage to artifical fractures can be eliminated because of no dreg.The fracturing fluid is composed of the cross linking agent of surfactant and the solution of anti ion salt in acid, which has small molecular weight, and does not contain any high molecular weight, presenting acidity. During fracturing, it makes the matrix acidification around the artificial fractrues, so the extent of the acidification is increased largely, which can not only acidize the matrix near the wellbore and remove the damage of the area, but also can remove the permeability damages near the matrix with propagation of the fractures.The fracture finally created is not a simple main fracture seepage passage, but a permeable belt along the main fracture, the width of which is significantly larger than that of the main fracture, improving thoroughly the areas'permeability near the wellbore and fractures,Based on the congregation principle of viscoelastic surfactant, an acid-resisting surfactant is synthetized, the system of which is Gemini. After optimizing the compostions, the compounding formula of acidity fracturing fluid is formed. After the performance test of the system, its temperature rating and resistance to shear capabity meet the needs of a area in Daqing Oilfield. The damage of the system to the core is less than 20%, and the permeability of some corbonate formations is increased even. Because of applying acid after pumping, the corrosion of acid to fracturing equipment is prevented, solving the technical difficulties of equipment corrosion of acid during fracturing, and is beneficial for the safe implementation of the acidity fracturing fluid in the field.Clear and high efficient fracturing liquid is the key factor to ensure work safely and raise fracturing effect. Scientific operation monitor and analysis system will be important tool for raising efficiency,modifing fracturing design and studying fracturing effect.According to the formation feature of an oil field in Daqing and the properties of flowage,filtration,viscosity-temperature and gelout of our new fracturing liquid of free damage,some models have been established,such as pseudo-three-dimensional model to simulate the extend of fractures,the model of the distribution of proppant migration,the model of wellbore flow,the model of temperature field,the model of liquid filtration and so on. By building database,the data explanation is more scientific.By the study of data acquisition and communication,portable acidizing and sand hydraulic fracturing monitor has been developed. We build monitor and explanation software system. The center of software system is data. The main body is visual operation. The whole system is designed with modules. The calculation is stable and reliable. Data acquisition and communication is fast. It is satisfied with the commercial requirements.Acid treating and sand fracturing have obvious shortcomings. Fracturing fluid of free damage puts acid treating and sand hydraulic fracturing together. The development of real-time explanation and monitor system realizes the operation of acidizing and sand hydraulic fracturing,real-time monitor,data analysis,stimulation technology of single well of operation and adjustment incorporation.The surfactant acidic fracuring fluid system not only can remove the damage and scaling near the wellbore area, but also can release the formation damage caused by fracturing fluid in the filtration belt near the fracture wall to reduce seepage resistance in wider range. Meanwhile, when the fracturing fluid system contacts with oil, gas and formation water under the formation temperature, it will break gel automatically without residue left, and will be flowed back thoroughly. The fracturing system has been used in 5 fields tests of Daqing Oilfield, improving the wells'oil productivity in low permeability calcium sandstone, and obtaining significant results. The system is a very promising technology.