33 results about "Wellbore instability" patented technology

A method and computer program product of either preventing or minimizing pore pressure increase near the wellbore wall within argillaceous formations through which a borehole has been drilled. By interpreting relevant drilling experience data, the type, extent and time-dependency of wellbore instability mechanisms are determined. The impact of drilling mud designs on the time-dependent wellbore instability and hole enlargement is determined by back-analyzing observed drilling events. At least one field-based criterion relationship between net mud weight reduction percentage ratio and hole enlargement is determined. A maximum allowable percentage ratio(s) of net mud weight reduction and either breakout mud weight or mud weight used for the adopted maximum hole enlargement that the wellbore may experience during drilling is determined. Drilling mud salinity value and salt type to satisfy maximum allowable percentage ratio(s) is then determined.

A process for reducing wellbore instability includes inputting pre-drilling assessment information into an hydraulics analysis and wellbore stability application, inputting a well plan into the hydraulics and wellbore analysis application, inputting a parameter measured at the wellsite into the hydraulics and wellbore stability analysis application, inputting an observation made at the wellsite into the hydraulics and wellbore stability analysis application, integrating the pre-drilling assessment information, the measured parameter, and the observation into the wellbore strengthening analysis application, and adjusting a drilling fluid parameter in response to the integrated pre-drilling assessment information, the measured parameter, and the observation.

The invention discloses a method for forecasting a weak plane formation collapse pressure equal yield density window. The method sequentially includes the steps: dividing a weak plane formation into a compact section and a crack section according to characteristics of the weak plane formation; testing the strength of a rock body and the strength of a weak plane of a rock by the aid of the triaxial compression test of the rock; inverting stress distribution and pore pressure distribution of surrounding rocks of a compact formation well by the aid of a fluid-solid coupling model, and determining the lower limit of the collapse pressure equal yield density of a compact formation according to Mohr-coulomb failure criteria; analyzing the failure state of the surrounding rocks of the weak plane formation well according to the rock weak plane failure criteria, and determining the lower limit and the upper limit of the collapse pressure equal yield density window of a crack formation; building a weak plane formation collapse pressure equal yield density window calculation model, substituting parameter values into the model and then determining the weak plane formation collapse pressure equal yield density window. The weak plane formation collapse pressure equal yield density window can be forecasted before drilling, so that drilling fluid density is reasonably selected, and wellbore instability is effectively stopped.

The invention relates to a strong inhibitive drilling fluid for drilling shale for shale gas development and solves the problem of wellbore instability, and hydration collapse of the shale stratum is inhibited. The technical scheme of the strong inhibitive drilling fluid is that the the drilling fluid is prepared from the compositions of, by mass unit, 900-1,000 g of tap water, 30-60 g of bentonite for drilling fluid, 2-4 g of Na2CO3, 0.3-1 g of strong inhibitive filtrate reducer JT900 for drilling fluid, 0.5-1 g of potassium strong inhibitor FK-1, 2-5 g of coating agent FK-421 for drilling fluid, 1-1.5 g of shale inhibitor NF-923, 1-2 g of positive ion viscosity reducer XH-1, 2-3 g of shale stabilizer DLSAS, 4-6 g of reservoir shielding agent QCX-1, 2-4 g of blocking agent DE-1 and 0.5-1 g of lubricant RT-881 for drilling fluid; finally, the alkali liquor with the mass percentage concentration of 40% is prepared by adding water to NaOH, the system PH is adjusted to be 8.5, the drilling fluid weighting agent baryte is used for weighting the the system density to be 1.8-2.0 g / cm<3>, and the drilling liquid is prepared. The drilling fluid system has small environment pollution, and the drilling liquid has excellent rheological property and high sealing capacity and is used for drilling the shale.

The invention discloses a clay inhibitor for drilling fluid and a preparation method thereof. The clay inhibitor is made of the following raw materials in parts by weight: 40-80 parts of nano-hydroxide aluminum, 30-60 parts of inorganic salt, 70-120 parts Polyacrylamide, 5-10 parts of ferrous chloride or ferrous sulfate, 50-100 parts of sulfonated nitrohumic acid, 20-50 parts of lignosulfonate and 8-15 parts of potassium chlorate; its preparation method is: Mix and stir sulfonated nitrohumic acid, lignosulfonate, potassium chlorate, ferrous chloride or ferrous sulfate, react at 80-100°C for 1-1.5h, then adjust the temperature to 35-40°C, adjust The pH value is 9-11, then adding nano-hydroxide aluminum and inorganic salts in sequence, stirring for 20-30 minutes, adding polyacrylamide, and stirring at 50-60°C for 2-3 hours to prepare an inhibitor for clay. The invention has the advantages that the prepared clay inhibitor can be applied to water-based drilling fluid, has a strong ability to inhibit clay hydration expansion, and can alleviate the phenomenon of well wall instability.

The invention belongs to the field of reservoir reconstruction in the natural gas hydrate development process, and in particular relates to the theory and realization method of reinforcement and anti-slump and sand prevention in the natural gas hydrate stratum. The present invention combines stratum reconstruction with fracturing and grouting reinforcement technology, through the fracturing and grouting process, cracks appear in the natural gas hydrate formation, and the solidified liquid enters the cracks and goes deep into the formation through the pressure difference, forming a "rib" structure And it is a reinforced body with certain strength and permeability, which supports and prevents the formation from collapsing and sand. In the present invention, through the analysis of the physical parameters of the target formation, the use of the curing agent system, the regulation of the fracturing construction process and the pumping of the solidification liquid into the formation during the fracturing process, the purpose of strengthening and preventing collapse and sand prevention in the natural gas hydrate formation is realized, forming The reinforced body can be well cemented with the surrounding formation, effectively avoiding sand production caused by hydrate decomposition, and well wall instability caused by formation collapse.

A polymer cleaning drilling fluid system, which is made of the following raw materials: tap water, bentonite, sodium carbonate, sodium hydroxide, fluid loss reducer, wall solidifying agent, coating agent, polyanionic cellulose, high temperature resistant Salt fluid loss reducer, lubrication inhibitor, solid lubricant for drilling fluid, solid lubricant graphite, KCl, gel plugging agent, ultrafine calcium carbonate powder, weighting agent barite powder. The preparation method of the fluid loss reducer and the wall-fixing agent is also provided. FL after aging at 180°C in the present invention HTHP ≤13mL, 8h linear expansion reduction rate ≥80%, cuttings rolling recovery rate ≥92%, mud cake adhesion coefficient ≤0.1, it has good fluid loss control performance, inhibition performance and lubricating performance, suitable for sand-shale mixed layer Drilling of deviated or horizontal sections of formations. The invention has good comprehensive performance, low cost, environmental protection, effectively solves the problem of well wall instability easily caused by water-based drilling fluid in the drilling process, and is beneficial to wellbore cleaning, reservoir cleaning and environmental protection.

The invention discloses a method for quantitatively evaluating the risk of wellbore instability in complex formation drilling, including: determining geomechanical parameters and rock mechanical parameters; obtaining distribution fitting results of the geomechanical parameters and rock mechanical parameters; Calculate the distribution fitting results of parameters and rock mechanics parameters, obtain K-S test values ​​and sort them; conduct correlation analysis on geomechanics parameters and rock mechanics parameters to obtain a correlation coefficient matrix; establish a reliability evaluation model for wellbore instability risk; According to the K-S test value and the correlation coefficient matrix, Monte Carlo simulation is carried out and brought into the wellbore instability risk reliability evaluation model to calculate the wellbore instability risk. The invention fully characterizes the uncertainty of parameters by using well logging data or indoor experiment results, especially considering the correlation between various parameters, so that the samples obtained by Monte Carlo sampling are more accurate, and the risk assessment of well wall instability is improved. accuracy.