Degradable preformed particle gel as temporary plugging agent for low-temperature unconventional petroleum reservoirs:Effect of molecular weight of the cross-linking agent

The development of unconventional petroleum resources has gradually become an important succession for increasing oil production.However,the related engineers and researchers are paying more and more attention to the application of temporary plugging agents(TPAs)for their efficient development.TPAs can expand the stimulated reservoir volume(SRV)and facilitate the flow of oil and gas to the bottom of the well.Particle-gels used as temporary plugging agents have the characteristics of the simple injection process,good deformation,high plugging strength,and complete self-degradation performance,which have been widely applied in recent years.In this paper,five samples of DPPG polymerized by different molecular weights of cross-linking agents were prepared.In addition,infrared spectroscopy analysis,differential calorimetry scanning(DSC)analysis,static particle gel swelling and degradation performance evaluation experiments,and dynamic temporary plugging performance experiments in cores were conducted at 34°C.Results show that as the molecular weight of the cross-linking agent(at 0.01 g)in the DPPG molecule decreased from 1,000 to 200 Da,the fewer cross-linking sites of DPPG,the looser the microscopic three-dimensional mesh structure formed.The swelling ratio increased from 7 to 33 times.However,the complete degradation time increased from 40 to 210 min.Moreover,the DSC results confirmed that the higher the molecular weight of the cross-linking agent,the worse is chemical stability and the more prone it to self-degradation.DPPG samples had good temporary plugging performance in reservoir cores.DPPGs prepared by the cross-linking agent with smaller molecular weight has a stronger swelling ratio,higher gel strength,and greater plugging strength in the core permeabilities.Moreover,the degraded DPPG is less damaging to the cores.However,their slower degradation rates take a slightly longer times to reach complete degradation.The results of this paper can provide new ideas and a theoretical basis for the development of particle gel-type temporary plugging agents(TPA)with controllable degradation time in low-temperature reservoirs.It can help to expand the application range of existing DPPG reservoir conditions.

Degradation of Disposal Hydroxyl-Terminated Polybutadiene Composite Solid Propellant

With the greatly increasing amount of discarded hydroxyl-terminated polybutadiene(HTPB)propellant year by year,it is of high significance to study the safe,efficient and environmental processing method of disposal HTPB propellant.In this paper,the decomposition agents are formulated for degrading the waste composite solid propellant.It is found that the following formulations of butanone 25%-55%,xylene 30%-75%,deionized water 40%-45%have effective influence on the degradation of the waste composite solid propellant.The proper degradation time is found to be about 7-8 h.With the help of infrared spectrum analysis,scanning electron microscope imaging,thermogravimetric analysis and solvent viscosity test,it was proved that after degradation reaction on the propellant sometimes,a large number of irregular fractures occurred in bulk resulting from effective degradation.The characterization of the propellant after degradation showed that the hardness of the propellant decreased,the viscosity increased,and a large number of holes and cracks appeared on the surface.The results showed that the formulated degradation agent and degradation condition perform good degradation effects on HTPB solid propellant.

Influence of morphology on basicity of CeO2 and its use in 2-chloroethyl ethyl sulfide degradation

Three CeO_2 samples with different morphologies, i.e., cubes, rods, and spindles, were synthesized and investigated for 2-chloroethyl ethyl sulfide（2-CEES） degradation. The samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, the Brunauer-Emmett-Teller method, and temperature-programmed CO_2 desorption. It was found that morphologies of CeO_2 could strongly affect the surface properties and the 2-CEES degradation activities. The surface basicity and the continuous 2-CEES degradation activity of spindle-like CeO_2 were much better than those of the other CeO_2 samples, although all the samples had identical chemical compositions. That was benefited by the largest surface area, abundant microcracks, and surface oxygen vacancies of the spindle-like CeO_2.

Construction of hierarchically porous metal-organic frameworks via vapor atmosphere etching

Developing a versatile etching strategy for constructing hierarchically porous metal-organic frameworks(HP-MOFs)with anticipated mesopores and micropores remains a crucial scientific challenge in probing the enhanced performance and potential applications of MOF materials.Herein,a universal vapor etching method is implemented to controllably create HP-MOFs.Based on the principle that the concentration of vapor is lower than that of the solution,the etching rate and strength toward MOFs are greatly reduced,enabling us to obtain intermediate products during etching.Using this strategy,a series of desired HP-MOFs with varying metal nodes have been prepared.The resultant HP-MOFs integrate the merits of mesopores(mass transfer facilitation)and micropores(large internal surface area).For the degradation of the nerve agent,dimethyl 4-nitrophenyl phosphate,HP-UiO-66 exhibits better catalytic activity than pristine UiO-66.