Short Radius Horizontal Wells Screw Drill Mechanical Properties Analysis

With the continuous exploitation of oil fields and frequent workover operations, the conditions of oil and water wells have become worsen, and, in addition of the anisotropic reservoir, the enhancement of the recovery ratio of the oil fields was badly influenced. Adopting the technology of medium-short radius horizontal well drilling may not only reduce the cost of drilling, but also increase the exposed area of the reservoir, therefore the recovery ratio, economy and efficiency can be enhanced. Especially, many main oil fields in the east of china one after the other turn into high water-cut term and have a lot of old wells that are abandoned or stopped production every year, so adopting the technology of the medium-short radius horizontal well also has a significance for the strategy of petroleum and energy.This paper investigates the bit side force and deflection of positive displacement motor (PDM) with bent housing(s) in the crooked well. Adopting the theory of elastic mechanics, this paper presented a model to calculate the deflected angle at the both ends of the elastic beam with two different stiffness drill stems in the same stride. Then the side force at the bit. and balanced curvature of Bottom Hole Asembly (BHA) with PDM can be determinded.This paper calculated the side force at the bit of Φ 120mm å'ŒÎ¦165mm PDM with bent housing(s) under the different parameter of structure (then bent angle and the position of the bend sub, the diameter and the position of the stabilizer(s), the geometrical parameter of the well bore (the inclination at the bit, the curvature of the well bore), the parameter of the drilling technics (primarily the weight on the bit). By limiting curvature, this paper forecasted the build rate of PDM with bent housing(s). This paper also analyzed the possibility of running the PDM with bent housing(s) into Φ 139.7mm and Φ 177.8mm casing .Based on the force at the bit and deflection of BHA and the rock-bit interaction, this paper set up a new type of well trajectory prediction model that is testified by field data.Research results indicated that the build rate and limiting curvature of PDM with bent housings are strongly related to the parameters including the angle of the bend, the diameter and the position of the stabilizer(s) (or the high of the pad), the weight on the bit, inclination at the bottom of a well. The bigger the angle of the bend and the higher the pad, the larger the side force at the bit and the larger the limiting curvature. The weight on the bit and the angle of inclination have a little influence on the mechanical performance of the little size PDM with bent housing(s) in the medium-short radius horizontal drilling. The possibility of running the PDM with bent housing into casing is different.: Φ89 mm PDM with pad and the double bent housings (the combination of bent angles is 3°×2°) can smoothly run into Φ139.7 mm casing,;but running Φ120 mm PDM with single structure bent housing (bentangle is 3.5°) into 0177.8 mm casing is difficult and the force is applied to press BHA with bent housing(s) into the hole. The conclusions can provide a reference on forecasting the build rate, choosing the parameter of structure of the PDM with bent housing(s) and designing the reasonable drilling parameters of PDM with bent housing(s).