| With the over exploitation of the earth shallow resources and world energy demand increase, people have to put the drilling target from epicontinental sea to the abysmal sea, from shallow to deep, deep and ultra-deep well drilling has become an important direction in the drilling industry development. Due to the well deeper, more technically difficult, therefore, all countries in the world make the drilling depth and speed as an important sign of the technological level of the drilling process.Requirements for drilling fluid to deep drilling not just the amount of accumulated but also the improvement of quality, Is different from the shallow well drilling fluids but a new drilling fluid systems and technology, Currently deep water-based drilling fluids rheology control remains a major technical problems currently not well drilling technology solution, When the high temperature, high salinity, high-density exist, Rheological properties and dehydration wall building performance of the drilling fluid, is more difficult to control, as demonstrated by low and high temperature rheology is difficult taking into account, HTHP water loss is large and thick mud cake. Therefore, Further research the mechanism of action which the water-based drilling fluid technology can meet three requirements of the high temperature (>180℃), high salinity and the high density (>2.00g/cm3).The formation of new theoretical understanding, Guidance of high temperature and density of water-based drilling fluid technology to improve and enhance, To meet the drilling technology needs of the complex formation of deep wells safe, fast, high quality, efficient, So that our drilling technology has reached world advanced level is very important.Contents of this paper is the latter part of China National Petroleum Corporation in scientific research and technology development projects:Research on new methods and technologies of drilling sub-topic"high-temperature (>180"C), high salinity (up to saturation), high density (2.00-2.50) water-based drilling fluid control theory and application technology research," The first half of the project’s completion studies of fluid loss agent of temperature of200℃anti-salt (saturated), The performance of low-density high-temperature and high salinity drilling control using a small amount of several agents have been able to deal with a good solution, But when the drilling fluid density increased to more than2.00g/cm3, Performance of drilling fluid system is still difficult to maintain. Particularly serious deterioration of rheological properties, Meanwhile, its performance is often HTHP build walls along with destruction. Resulting in even high temperature, high salinity clearance of low density fluid performance, High-density fluid performance after the aggravation of the situation is still difficult to pass. Become a high-temperature water-based drilling fluid technology caused this failure solved major technical problems. Past, people focused their attention on the development of high-temperature viscosity agent treatment agent Although some of the results obtained, But at home and abroad has not yet been a breakthrough.Through theoretical analysis and laboratory experiments, in-depth study the influencing factors and control theory of sedimentation stability,fluid rheology and dehydration wall building performance of high-density water-based drilling, Particularly the presence of high concentrations of barite particles made a serious impact of Drilling fluid rheology and HTHP wall made of, Obtained the following knowledge and results:1) When the drilling fluid barite particle concentration increases, Its inter-particle interactions exist (no longer "inert"), As the particle concentration increases, Interaction between the particles and the stability of the state changing and so complex changes occur. Can be divided into three different phases:Free settling stage, Compression settlement stage, And the transition between them. The study also found:The Action of between the high concentration of particles of barite in High density drilling fluid, Not only have a major impact on drilling sedimentation stability, But also directly increase the drilling fluid shear force static and dynamic shear and the apparent viscosity of the drilling fluid.2) The study found that with the increasing density of the drilling fluid, After concentration of the drilling fluid reaches a certain value barite particles, Barite particles flowing probability of a significant increase in direct contact Close contact friction between the particles along with a sharp increase, In addition to increasing the viscosity becomes unstructured outside the new flow resistance can not be ignored. Thus, the apparent viscosity of the drilling fluid is no longer just a high-density "Structural viscosity" and "non-structural viscosity" theory that the two parts of the existing constitution,But rather consists of three parts:That apparent viscosity=non-structural viscosity (viscosity liquid+solid phase particles-liquid interface friction between...)+structural viscosity (clay particles card house structure, Polymer clay particles mesh)+solid-phase particles (close) contact with the friction caused by the viscosity of... The study found that according to dense particle accumulation principle, System containing particles of the same quality, They surface contact state and status, Does not depend on the dispersion of particles in the main, The distribution of the particle dispersion of the series have a great relationship. Particle size distribution may be preferable to make it to a minimum. The use of "small particles caulking viscosity principle" can greatly reduce this high flow resistance of the particle concentration in the fluid system (viscosity, shear). Meanwhile study confirmed:a certain size caulk small particles exist "rolling friction reduction" in the high-density drilling fluid system, May further reduce the original high density drilling fluid flow resistance.3) The study found that The main reason of high-density drilling fluid made it difficult to maintain good HTMP wall of water loss is the high-density drilling fluid system participate in the "build a wall" effect is mainly standard API barite particles74u m and a large number of very small (about1%) of sodium-micron colloidal clay particles. But this gradation is impossible to form a dense cake particles, unable to maintain excellent wall made of. Through the study found that optimization of barite grading can making clay colloidal particles with a tight heap, The larger accumulation density, The thinner the more dense cake, HTHP water loss is smaller, HTHP dehydration wall building better performance. For this reason, put into one to two intermediate particles during the API standard barite and clay colloidal particles, Weighting agent particles having a particle size (API standard barite) particle size0.05-0.15(near the lower limit), Plus greater than the weighting agent particles (API standard barite) plus the amount of1/4And for1%-2%of the colloidal clay particles.4) Optimization, integration of these research results.Presented simultaneously new principles and new methods of solve the major technical problems which hard to control high temperature and high density (p:2.00-2.50g/cm3) HTHP drilling fluid rheology and walls made of, On the basis of excellent resistance to temperature, salt-containing low-density drilling fluid with clay, Optimized weighting agent (such as barite) particle size distribution, The use of " small particles caulk viscosity principle " and caulk small particles "rolling friction-reducing effect," and "close the dump " made wall principle, Effective control of both high temperature and high density (p:2.00-2.50g/cm3).Effective control of both high temperature and high density (P:2.00-2.50g/cm3) drilling fluid rheology, HTHP well maintained and its walls made of. To solve the high temperature and high density (P:2.002.50g/cm3) HTHP drilling fluid rheology and walls made of hard to maintain good control of this major technical problems to provide effective support for the theoretical and experimental basis. Application of this principle can be relatively easy to get a high-temperature high-density water-based deep saturated brine drilling fluid system and evaluated.5) Thus, As long as excellent properties of low-density water-based drilling fluid in the high temperature, high salinity,On its basis, Application of the above principle, Optimized weighting agent (such as barite) particle size distribution, Even if no other anti-temperature viscosity reducer added, Fluid loss control agents are also able to establish excellent high temperature performance, high-density drilling fluid system, Thus greatly simplifying the formula drilling fluid system, reducing the dosage of additives, Simplifying the application process, To provide a convenient site construction, reducing costs. |
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