Research On The Micro-foaming Drilling Fluid System And Application In Tamtsag Oil Field

The permeability of reservoir in Hailar-Tamtsag basin is low and extra low. Drilling inthis district is rather difficult, and the drilling speed is rather low. The conventional drillingfluid invades easily account for serious damage, or even lost the ability of production. So newdrilling fluent needed to be researched. Micro foam drilling fluid is a kind of low densitydrilling fluid system which regards the water base as the continuous phase, and foam as thedispersed phase, which can prevent the well wall collapse and provide higher drilling speed.The Micro foam system can also reduce leaking off rate, improve the rock-carrying capacityand protect formations. It has great ability whereas the system is still under the research andexperimental stage, the application in Tamtsag oil field situation is not known yet.This paper analysis Tamtsag oilfield Geology, the sedimentary feature, reservoirdevelopment characteristics and lithologic characteristics of Tamtsag oil layer. Establishingthe study on the performance of micro foam drilling fluid system to observe themorphological characteristic of the micro foam; using the power law model to describe therheological characteristic of the micro foam drilling fluid system and obtain the influence ofthe gas content of drilling fluid viscosity; Chemical stability of the micro foam was Measured,results indicated that the micro foam has a good chemical stability; With the help of infraredspectrum, electron microscope and transmission electron microscopy (sem) instrumentsanalysis, we discovered that micro foam has the ability to plug temporarily, improve the leakof fluid and prevent well wall collapse which can effectively protect the reservoir. Thelaboratory test of foaming agent and foam stability proves that micro foam system has goodcharacteristics of temperature resistance, calcium resistance, clay pollution resistance, etc. Setup the model of drilling fluid temperature, pressure and density during the drilling process.Collapse mechanism was analyzed by the conditions of borehole wall instability, combinedwith the micro foam system’s characteristics that low density, high shear viscosity, strongbridging plugging capability and hydrophobic lipophilic property. The mechanical model offoam in micro fractures was established to analyze slugging and leak off prevention. Leak offtest shows that leakage time decrease when there is only the instantaneous leakage, and itplays a key role in the collision process. Improve drilling rate mechanism of Micro foamsystem was studied by analyzing lower the cutting pressure instated strength of rock, andchanges in rock surface properties.The optimization of micro foam drilling fluid formulation preformed in the Tamtsagoilfield.207wells were applied. The results show that the percent of well leak rate decreasedby5.23, the average penetration rate increased by30.02%and direct economic benefitsreached162.1609million Yuan. Practice has proved that micro foam drilling fluid technologyreduces the probability of well leakage accidents, raises the drilling speed and works well inthe Tamtsag oilfield.