传统的数字岩心建模方法建立的数字岩心模型尺寸单一,分辨率固定,导致存储空间过大,难以维护等问题.因此,提出了一种分层四叉树模型,给出了模型的构建及扩展方法,基于此模型,建立多分辨率数字岩心体素模型,同时在分层四叉树模型基础上,结合Marching Cubes移动立方体算法生成数字岩心面模型.通过实例检验证明,该方法建立的数字岩心模型极大地节省了存储空间,耗时较少,同时具有易于维护管理等优点.

Well Xuwen X3 is a multi-target directional well,deployed in Maichen depressed block in Beibuwan Basin.The section of the second spud has large wellbore diameter and long open-hole section with the length of 2 667 m.The open-hole length of the third spud is 1 540 m.The geothermal gradient is high,and the electrically measured temperature is 211℃ in the depth of 5 974 m.The high geothermal gradient in the area affects the performance of MWD instrument,so multi–point measurement is necessary for lower formations,leading to wellbore trajectory control posterity.To achieve effect Well Xuwen X3 wellbore trajectory control,tapered hole assembly is used for the vertical interval,with length of 2 028 m,and the biggest hole angle is only 1.39 degree.For directional interval,the screw drill with 1.5 degree is used to orientate.In angle holding interval,the packed hole assembly and slightly building assembly are used.The four target points meet the drilling design and hole trajectory conforms to the demand of design,with the drilling depth of 6010m and the horizontal displacement of 2 017.22 m.It provides experience for similar well drilling operation.

Calcium carbonate scaling generally plays an important role in the reservoir permeability impairment in gas reservoirs of high CO2 content.Quantitative analyses were done on the factors(such as the solubility product of CaCO3 at certain condition,temperature,pressure,salinity of solutions,and pH etc.) affecting the solubility of CO2,and studies were conducted on the scaling mechanism of the gas reservoir in Jilin Oilfield(high CO2 content).Under high temperature/high pressure at bottom hole,pressure plays a more important role in the solubility of CO2,other factors such as the salinity of formation water,and pH also affect the solubility of CO2 to some extent.No scaling was generated in the reservoir before the invasion of the drilling fluid filtrate.Scaling(CaCO3) began to take place when the filtrate of drilling fluids having pH equal to or greater than 9 invaded the reservoir;thus,the pH of the filtrate should be as low as possible.

Air drilling has some advantages in enhancing ROP,minimizing downhole troubles,extending the service life of drill bits and improving the formation evaluation and so on.This paper discussed the minimum volumetric flow rate of air in air drilling and two design criteria,and the application of the calculation results in vertical well and directional well drilling.Examples of calculation were given in this paper.It was suggested that the calculation errors from the 2 volumetric flow rate calculation criteria were comparatively small,and were able to satisfy the field operation requirement.

Theoretical analysis and field application suggest that the invasion of liquid and solid of drilling fluids into fractures are the main reason for damage to fracture reservoirs.Extending "ideal packing theory" to fracture type reservoir protection and optimizing the ideal packing agent and film-forming agent,a carefully designed ultra low osmosis water based drilling fluid by synergistic interaction was developed.Laboratory experiments show that this drilling fluid has better rheological property,higher temperature resistance and slicker mud cake which can form a homogeneous and compact seal coat on borehole.The API filter loss could be controlled under 2.3mL,and HTHP dynamic filtration was less than 0.3mL.Lab tests demonstrate that this system can effectively improve fractured gas reservoir protection.

For the purpose of reducing drilling fluid expense and solving the problems occurred in Dagang Oilfield,including formation collapse,pipe-sticking,the positive-charged polyglycol/potassium chloride drilling fluids were optimized by orthogonal test designing software-SPSS13.0 based on the analysis of the formation clay and evaluation of the treating agent.Laboratory studies show that this fluid system has better inhibitive capacity,rheology,filtration,anti-pollution and lubricity.This paper also investigates the working mechanism of the mud and shows that positive-charged polyglycol and potassium chloride have synergistic effects,which helps hole cleaning and wellbore stability.