Study On The Properties Of Sintered Wall Materials Prepared From Shale Gas Water-based Drilling Cuttings

As shale gas drilling progresses in China,water-based drilling fluid systems have been widely used in complex deep well drilling projects,resulting in a huge amount of water-based drilling cuttings(hereinafter referred to as water-based cuttings).Most of these cuttings are treated by wind-drying landfill or solidification,and only a small portion is reused.This treatment method not only increases the risk of environmental pollution,but also wastes the resources of water-based cuttings.Therefore,this article uses water-based cuttings as raw materials to produce sintered bricks,solving the problem of cuttings disposal and achieving the reuse of water-based cuttings as a sintered wall material resource,which has significant ecological environmental protection and sustainable development significance.This article first starts with the physical and chemical properties of water-based cuttings,and compares and analyzes the chemical composition,mineral composition,particle size composition,and plasticity index of water-based cuttings and ordinary brick-making raw materials,to explore the feasibility of using water-based cuttings to produce sintered bricks.Then,the characteristic pollutants and radioactive elements of water-based cuttings are compared with relevant standards,and it is determined that the production of sintered bricks from water-based cuttings will not harm the environment and human health.Subsequently,through single-factor experiments,the influence of different process conditions(water-based cuttings content,sintering temperature,heat preservation time)on the properties of sintered bricks(compressive strength,water absorption rate,bulk density,linear shrinkage rate)is determined,and the sintering mechanism and experimental phenomena are analyzed by XRD and SEM.Finally,the optimal sintering regime is determined by adjusting the sintering temperature and heat preservation time.On the basis of sintered bricks,the simulated parameters of the sintered bricks under the optimal preparation conditions,such as bulk density,thermal conductivity,elastic modulus and Poisson’s ratio,are tested.Using Fluent software,the influence of pore aspect ratio,pore row number,pore column number and porosity on the equivalent thermal conductivity of sintered porous bricks is investigated,and the principles of optimizing the pore type of sintered porous bricks are summarized.Combined with the pore type regulations in the "Sintered Porous Bricks and Blocks" GB13544-2011 standard,six optimization schemes for pore types are designed,and finite element analysis software is used to analyze the nonlinear structure and three-dimensional steady-state heat transfer of the designed porous bricks.On the basis of comprehensive consideration of strength,strength-toweight ratio and thermal properties,the optimal pore type structure is determined.The main research results are as follows:(1)The main chemical composition,mineral composition,particle size composition,and plasticity index of water-based cuttings meet relevant brick-making standards,and it is feasible to use water-based cuttings to produce sintered bricks.(2)The leaching concentration of pollutants from water-based cuttings is lower than the corresponding standard requirements,and it is not a hazardous waste,nor will it cause secondary pollution.The radioactive indicators of water-based cuttings meet the standard requirements and can be used as raw materials for building materials without harm to human health.(3)When the water-based cuttings content is 20%,the sintering temperature is 1000°C,the heat preservation time is 2 hours,the moisture content is 12%,and the coal-to-material ratio is 1:8,the properties of the sintered bricks produced meet the requirements of MU20 in the national standard "Sintered Ordinary Bricks"(GB/T5101-2017).(4)Increasing the length-to-width ratio of pores,increasing the number of pore rows,reducing the number of pore columns,and increasing the porosity are all beneficial for improving the thermal properties of porous bricks in the direction of heat conduction.Among them,increasing the number of pore rows has the most significant effect on reducing the equivalent thermal conductivity,while increasing the number of pore columns has little effect on the equivalent thermal conductivity.(5)Six self-designed porous bricks completely meet the requirements for pore type,pore structure,and porosity in the national standard GB13544-2011 "Sintered Porous Bricks and Porous Blocks".Considering compressive strength,strength-to-weight ratio,and thermal resistance,TYPE V is the best pore type,with a porosity of 29.93%,large pore size of33mm×10mm,small pore size of 12.5mm×10mm,horizontal rib width of 11 mm,vertical rib width of 8mm,hand-grab hole size of 75mm×30mm,horizontal outer wall rib thickness of20.5mm,and vertical outer wall rib thickness of 17 mm.