Theory On Cementing & Channeling Resisting And Application Technology

Cementing and channeling resisting, are key technologies in drilling and completion of oil and gas wells. They are related to the successful implementation of drilling, completion, fracturing, acid treatment and perforation. Large area high-pressure water injection, especially in adjusting wells, the original pressure system was changed, and forms one or more high pressure layers, normal pressure layers and underpressured layers at different depths in a well. Casing shears and unbalanced injection-production system further complicates the situation.Water seepage increases quickly. All these complicated geological conditions are serious obstacles to satisfactory cementing of oil & water wells. It slows down the effective implementation of production programs. In addition, in order to improve productivity of oil and gas wells, especially in low pressure, low permeability oil and gas reservoirs, some stimulation treatments were carried out. In order to extend the perforation range a charge with more explosive energy than ever used before was used. The resulting impact affected bond quality of cement sheath and cement sheath between borehole wall and casing.In this article, the following properties will be described, the compression-dilatation properties of cement sheath, cementing displacement ratio, regularity of water-gas channeling, effecting factors of water seepage to cementing quality, perforation damage to the cement sheath. By integrating theory derivation with the testing data verification, this thesis focuses on the factors affecting cement quality, and searches for the methods of improving cementing quality.The main content of this thesis are as follows:(1) The compression- dilatation property of cement sheath:Designed and built the ring linear dilatation test system and cement sheath strain test system. Tested the compression-dilatation properties and compressive strength of cementing stone in permeable and impervious conditions. Tested the effects of different layers to the compression-dilatation properties of cementing stone.(2) The theory of cementing displacement:Analysis of the rheological property of non-Newtonian fluid, and the flow and displacement properties of cementing slurry in casing and borehole. Wrote the constitutive equations; discussed the reason and theory of the"U"tube. Designed and made an equivalent modeling borehole, searched for the effects of casing eccentricity, borehole expanding rate, displacement capacity to the displacement ratio by test.(3) Water-gas channeling regularity in an annular borehole after cementing;Designed a gel strength test meter and gas channeling simulator, tested borehole permeability to weight loss, gas channeling of cementing slurry, and temperature to gas channeling of cementing slurry. Presents the concept of stable pressure coefficient and quantitatively describes the stable pressure in the high pressure layer.(4) The effects of water seepage on cementing quality: Designed a water seepage simulator. By use of this simulator, studied the effects of pressure drawdown on the hydrostatic column, pressure in annular and formation pore and how this affects cementing quality. Studied the effects of water seepage flow rate on cementing quality, found the critical flow rate and provided the technical reference for controlling the formation pressure.(5) Impact resistance of cementing sheath:Designed the real bullet perforating simulation equipment; introduced the concepts of"dynamic elastic modulus","broken absorbed energy"and"dynamic fracture toughness"to describe the impact resistance of the cementing stone. This is the first time that the Hopkinson instrument has been used to test the dynamic mechanical properties of nonmetal materials.(6) Application of the technology:According to the results of the research, channeling resisting cementing slurry was developed together with a weight spacer, impact resistant cementing slurry and a dilatation cementing slurry. All the cementing additives were tested using well site experiments. They have satisfied the demand for cementing operations and are used to improve the cementing quality.This thesis focuses on factors affecting cementing quality and presents the compression- dilatation theory of cementing stone. Developed the rules for water-gas channeling, water seepage and impact resistance of cementing stone are also explained in this thesis. Providing a technological guarantee for oil and water well cementing and especially for the adjusting of wells, but also, be helpful in cementing technologies. As a technological treatment, it improves the stable pressure and displacement ratio, and improves production.