Preparation And Evaluation Of Foam Fracturing Fluid

With the continuous development of China’s economy and science and technology, the oil and gas reservoir exploration and development technology have been greatly improved. China has proved a lot of low permeability oil and gas reservoir and low pressure and low permeability oil and gas fields of China’s reserves continued to increase. Fracturing fluid is an important measure for low permeability and ultra low permeability oil and gas reservoir reformation. It is great significant for China’s oil and gas reservoirs to develop advanced fracturing fluid.Foam fracturing fluid is what is used in the process of hydraulic fracturing, with all kinds of material as the dispersion medium and carbon dioxide, nitrogen and air as dispersed phase and various additives added. Foam fracturing fluid is easy to flow back, has small damage and good sand performance. It is suitable for low pressure and low permeability reservoir.This article studied four kinds of surface active agent(AS, AE, AG, CA)and combination of CA/AS, AS/AG, AE/AG, CA/AG as foaming agent. And I chose long chain alcohols, surfactant, polymer three kinds of foam stabilizing agent, including LS-1, LS-2, LS-3, WA-1, WA-2, YA-1/LS-2 and YA--2/LS-2 six as a foam stabilizer, and xanthan gum, hydroxypropyl guar gum, hydroxypropyl methyl cellulose (HMPC), hydroxyethyl cellulose (HEC), polyvinyl alcohol 1788 (PVA1788), carboxymethyl cellulose (CMC) of six kinds of polymers as stabilizer. The foam fracturing fluid with different formulations were assessed by foaming rate and half-life. The foam fracturing fluid with good foaming ability and stability were screened. I selected CA as foaming agent, YA--2/LS-2 as foam stabilizer, quality of which is 2:3. The foam fracturing base fluid consists of foaming agent and foam stabilizer with the ratio for 5:1.1 selected guar gum as stabilizer with 0.2%. The base liquid’s concentration in stabilizer solution was 1%. The compatibility of foam fracturing fluid with N2:rate of N2 was 200mL/min, and the base liquid’s concentration is 1%, which has the best foaming performance.This article evaluated surface tension of foam fracturing fluid, foam stability, resistance to high temperature and shearing, ability of carrying sand, mineralization degree experiment and compatibility with nitrogen. Surface tension of the foam fracturing fluid is lower than that of the same concentration of foaming agent and foaming ability is very good. The stability of foam fracturing fluid was evaluated using full automatic foam scanner. I found that using YA-2/LS-2 as foam stabilizer and hydroxypropyl guar gum as a stabilizer is efficient. After shearing at the condition of 120 ℃,170r/s, the foam fracturing fluid has good viscosity. The foam fracturing fluid has good carrying sand property. Mineralization degree experiment shows that the foam fracturing fluid had better salt tolerant, and effect of two valence ions on foam fracturing fluid is greater. The effects of nitrogen flow rate on foaming behavior of different concentrations of foam fracturing fluid has been studied. The wettability of foam fracturing fluid was studied. The contact angle increases at first and decreases later with the concentration of foam fracturing fluid increasing.Changes of the thickness of the liquid bubble size, bubble diameter with time and two-dimensional structure of foam was observed by electron microscope. This article discussed foam disintegration mechanism:liquid dischargement from bubble liquid film and gas diffusion between bubble liquid film.