Experimental and MD simulation of 3-dodecyloxypropanamine and 3-tetradecyloxypropylamine adsorbed onto quartz(101) surface

In this paper,two surfactants,3-dodecyloxypropanamine(DOPA) and 3-tetradecyloxypropylamine(TOPA),were synthesized and used as collectors in the quartz micro-flotation in the laboratory.Microflotation tests,FT-IR,XPS measurements,and ab initio Molecular Dynamics(MD) simulations were conducted to research DOPA,TOPA,and dodecylamine(DDA)'s adsorption mechanisms onto quartz(101)surfaces.The results of micro-flotation show that the adsorption of DOPA and TOPA onto quartz surface is more robust than that of DDA.The zeta-potential result shows that the DOPA/TOPA was adsorbed on quartz through electrostatic attraction.Then,MD simulation adsorption models were built to compare the computational properties of the three surfactants,such as the radial distribution function,and the interaction energies between the collectors and the quartz cleavage surface.The interaction energies of surfactants(RNH_(3)^(+) or RNH_(2)) on the quartz surface explained why the pH range of DOPA/TOPA is wider than that of DDA.XPS analyses and MD simulations confirmed that DOPA bonded with the(101) surface of quartz through three types of hydrogen bonds between the-NH_(2) of DOPA and the O atom of quartz.The hydrogen bonds of type A and type C were the most likely type and more potent than those of type B.

The formation bulk density prediction for intact and fractured siliciclastic rocks

The formation bulk density is one of the most important rock properties required for reservoir evaluation and geomechanical analysis.In intervals where the formation bulk density logs are not acquired,the industry practice is to estimate the formation bulk density from the compressional-wave velocity using empirical relationships.The major problems with the existing empirical relationships are:(1)they were developed primarily for specific lithologies(in most cases clean formations)and have failed to produce reasonable estimates when applied over a lithological column that consists of several stratigraphic units;(2)they are not applicable to rocks that contain microcracks/fractures.In this paper,a new formation bulk density prediction method that can be applied to a wide range of intact and fractured siliciclastic rocks is being proposed based on experimental data.The model is then validated using wireline log data acquired from an onshore well in the tertiary deltaic system of the Niger Delta basin.In the new model,the formation bulk density is expressed as a function of sonic velocity difference and shale volume factor.In general,an excellent agreement exists between the predicted and measured formation bulk density using the new technique.The statistical analysis shows that the new formation bulk density prediction model outperforms the most widely used empirical relationships with the least-root-mean square errors and least residual values.