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 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.