Fracturing Fluid Filtration Control Technology Research

Fracturing fluid is the core of the Fracturing process, its main function is cleave and transport proppant along fracture. The efficiency of the fracturing fluid will not only directly affect the dynamic geometry of the fracture, but also largely determines the success or failure of the fracturing construction, therefore, controlling the filtration of fracturing fluid is one of the keys of effective fracturing.The influences caused by fracturing fluid loss are great. In addition to reducing the liquid efficiency, the viscosity、rheological and other properties of the fracturing fluid will change significantly when the fracturing fluid occurs a great quantity of filtration, it may caused phenomenons such as sand plug and non-pumping of fracturing fluid when the filtration is serious, which increasing the difficulty of fracturing or even leading to fracturing failure; Secondly, a dense filter cake will be formed on the rock surface after a great quantity of fracturing fluid loss, the permeability of which is much smaller than the formation permeability, it blocks the flow of formation fluids to the fracture, at the same time, by occuping part or almost the whole gap between proppant, the filter cake can also causes great harm to the flow conductivity of the fracture; last but not least, the filtrate of fracturing fluid will cause varying degrees of damage to the formation, resulting in bad postfracture response. So the research direction of fracturing fluid loss control is finding a fluid loss control technology which can not only effectively control fluid loss but also reduce the damage to the reservoir.In this paper, study on fracturing fluid loss control technology is considered as the main line. Based on literature research, the paper firstly analyzed the present situation of research on fracturing fluid loss control technology, then conducteded the theoretical and experimental research on two aspects of conventional polymer fracturing fluid loss control technology and fluid loss control technology of newly fracturing fluid with no bottoms.In the traditional one-dimensional filtration model, the filtration mechanism of the conventional polymer fracturing was analyzed and summarized, as a result, three kinds of fracturing fluid fluid loss control mechanism and corresponding filtration coefficient are identfied, and the filtration coefficient Cw controlled by the building capacity of fracturing fluid is the focus of the study. Accroding to the experimental study on the conventional polymer fracturing fluid loss control technology, the fracturing fluid filtration law effected by several factors was found out; By analysising the experimental results, the existing problem and the contradiction what needs to be solved are put forward, in which the major contradiction problem is that the conventional polymer fracturing fluid can reduce the fluid loss while increasing the damage to the reservoir at the same time.The experimental studies on fluid loss control technology of a variety of fluid loss control agent showed that, the commonly used fluid loss control agents all seems to have good filtration reducing property, but the damage to the reservoir can not be ignored after using it, the damage rate of the permeability of reservoir matrix core and the flow conductivity of the propping fracture are high, so the fluid loss control technology of fluid loss control agents has not solved the contradiction problem between reducing fluid loss and reducing damage well,it needs to be further studied.For the fracturing fluid system with no building capacity, since the research in this aspect is less as it’s filtration mechanism and influence factors of fluid loss controlare different, which makes the study of the fracturing fluid loss control technology has certain limitation. Therefore, this paper has further studied on fluid loss controltechnology of newly fracturing fluid with no bottoms, according to the actual filtration situation of GRF fracturing fluid, a set of filtration rate measuring device which is suitable for this kind of fracturing fluid was designed and a feasible filtration rate measurement method was established. The filtration property of GRF fracturing fluid was evaluated by using the artificial core as filtration medium, it is proved to be well by the experimental results.A large number of theoretical and experimental results showed that:GRF fracturing fluid is a hydrophobic associating fluid, it has excellent viscoelastic behavior, it flows into the core pore with whole viscosity, it is able to build effective impedance with a little liquid when flowing through the porous medium, the fracturing fluid occurs viscoelastic response to the external liquid, resulting in high flow resistance called Filtration belt impedance R0, the stronger the viscoelastic is, the bigger the RO is. It is because of the effect of Ro, the fluid filtrating from the fracture to the reservoir is blocked, that’s make the filtrate speed of the fluid significantly reduced, so that the filtration ratein of the fracturing fluid is reduced. The stronger the viscoelastic of the fracturing fluid is, the better the filtration property of the fracturing fluid is.Conclusions are obtained by the study on influence factors of GRF fracturing fluid loss: Frist, GRF fracturing fluid shows good filtration property when the liquid permeability of the formation is lower than10×10-3μm2, but the filtration coefficient of GRF fracturing fluid increases much when the liquid permeability is higher than10×10-3μm-2,so it’s necessary to adopt auxiliary fluid loss control measures (such as injecting with nitrogen); Second, the influence to GRF fracturing fluid loss by pressure drawdown is small, which attributed to that GRF fracturing fluid can not formate filter cake when filtrating; Third, the influence to GRF fracturing fluid loss by temperature seems large, the higher the temperature is, the more serious the GRF fracturing fluid loss is. A large number of theoretical laboratory experiments and Field tests showed that:the fracturing fluid of GRF has a good filtration control performance, which is mainly determined by its viscoelastic, so the view of viscoelastic controlling filterloss is put forward.It is worth noting that, GRF fracturing fluid showed a significant low damage characteristic in the damage test experiment to the reservoir, it does little harm to the permeability of reservoir matrix core and the flow conductivity of the propping fracture, so it can control the filtration effectively while reduce the damage of fracturing fluid to the reservoir, that’s make it have considerable advantages and application prospect.In general, by studing on the fracturing fluid loss control technology, this paper summaried the advantages、disadvantages and limitations of a variety of fracturing fluid loss control technologies, we can provide an effective theoretical and experimental basis for optimizations of Fracturing fluid and fracturing operations.Anymore, a new fracturing fluid with no residue was founded, which can not only control the filtration effectively but also can reduce the damage to the reservoir to a large extent, it can provides new ideas for the filtration control technology of fracturing fluid and new research directions for fracture mining of the low permeability reservoirs and reservoir protection.