Mechanical Analysis Of Water Injection Pipe Column Of Large Displacement Well In Nanpu Oilfield

Separated layer water-flooding is an important technology that solves the contradictions of heterogeneous reservoir interlayer, improves oil displacement efficiency and keeps the oil field production stable. Nanpu Oilfield in eastern of Hebei is the nearly saturated complex fault block oil reservoir with the shortage of natural energy. So water injection has been a necessary technology to exploit the oilfield on the beach. Exploiting Nanpu Oilfield in eastern of Hebei mainly adopt artificial island. It just likes the CNOOC land exploitation mode. The well types are mainly composed of directional well and deep deviated well. Wellbore structure, complex borehole trajectory, and the span make the sealing of tubing string difficult in the separate injection process. So these cases also make the success rate of test decrease. Therefore, the deviated points in deep well are important to injection technology, especially for making an effective injection of on the beach. According to the well bore structure of well injected water in Nanpu Oilfield and production characteristics, we consider the related technical research results both at home and abroad and give full consideration to the domestic layered water injection technology, maturity of measuring technology and adaptability. Then we site operation factors, such as different well conditions and points to note to the layered water injection technical countermeasures.In this paper, based on the study of the layered water injection technology at home and abroad, we presented the strong sensitivity of reservoir water flooding and reservoir protection technology. This technology that was carried out in the complex layered water injection well is suitable for high temperature, high pressure, supporting tools exploitation, laboratory test and field test. The specific research work of this paper is listed below:(1) Based on the consideration of measured borehole trajectory, friction, viscous friction, tubing gravity, buoyancy, pressure inside and pressure outside, for comprehensive effect of layered water injection string in the large displacement well. And then three-dimensional "lever" and "soft rope" mechanics analysis models of water injection string of the large displacement well were established according to different influence of borehole curvature characteristics to tubing string stress in different part. According to the loading characteristics of the water injection string, we analyzed in detail their various effects in the wellbore, and established deformation calculation model of a large displacement well point of the water injection string which could reflect the stress of the water injection string.(2) Calculation model of the downhole tools was established according to consider the influence of temperature, pressure, gravity, and friction. Injection string stress testing instrument was developed, then the field measured data was used to demonstrate effectiveness of the model. The interaction among the downhole tools was considering in the model, which can be used to calculate stress condition for packer, anchor device, etc.(3) A simulation software using water injection string system of the large displacement wells has been developed, on the basis of the theoretical models of separated layer water injection string and the stress calculation models of tools mechanics. This simulation software can realize the functions of the string stress value in different conditions (lift down, water injection, a sealing and flushing, etc.), deformation of tubing string, and strength check on condition of wellbore temperature field, pressure field and different condition. And it also can provide the theoretical basis for optimization of string structure design, strength checking, feasible analysis of lift down and construction parameter, etc.