Isolation Membrane Water-based Drilling Fluid System

The isolation membrane water-based drilling fluid is a novel technology of working fluid in oil and gas wells. This technology is from the view of stabilizing borehole and controlling formation damage and based on the fundamental principle of transmitting substance and energy between borehole and formation. At the same time, combined with the new ideal and thoughtway of the physical and chemical stabilization borehole, the new system is expected to form the molecular membrane, namely isolation membrane, which can act as a barrier and prevent drilling fluid and filtrate from penetration. Furthermore, the barrier has restrained availably clay hydration swelling dispersion and borehole caving, then protect reservoir.Two major additives of the isolation membrane water-based drilling fluid, CMJ-1 and CMJ-2, are synthesized. Then their elementary structure is acknowledged by Infrared Spectroscopy (IR) and their physical and chemical performance are determined. What' s more, their performance in water-based drilling fluid of CMJ-1 and CMJ-2 are evaluated, such as the optimum adding amount the temperature resistant ability the tolerance to fouling lubricate and so on. The filtration loss controller, CSF-1 and the encapsulating agent, JH-1 matching the CMJ-1 and CMJ-2 are produced. Simultaneously, the viscosity reducer, JN-1 is optimized.Afterwards, according to above synthesis, evaluation and screening, the system of the isolation membrane water-based drilling fluid is optimized. And its typical formula are as follows: CMJ-1 system: 4%bentonite+0.6%CFJ-l+0.4%JH-l+l%CMJ -l+0.1%JN-l+NaOH(pH:9~ll); CMJ-2 system: 4%bentonite+0.6%CFJ-l+0.4%J H-l+2% CM J-2+0.1%JN-l+NaOH(pH:9~ll). In the same way, the property of the system is appraised. It shows that two systems owe 1) good rheology property and filtration properties; 2) strong inhibition; 3) good lubrication and strong EP film intensity; 4) outstanding the tolerance to fouling; 5) good sealing characteristic; 6) good ability of formation damage control; 7) the former excellent properties when the systems of CMJ-1 and CMJ-2 are high density( 1.25g/cm3 1.5g/cm3). Also, the performance of the isolation membrane water-based drilling fluid is very good and the major additives and the system are innoxious, which satisfies the demand of logging. And then, eliminating mudcake technology is researched.Finally, pilot study on mechanism of the isolation membrane water-based drilling fluid and eliminating mudcake is carried through.