Evaluating the effect of drill string rotation and change in drilling fluid viscosity on hole cleaning

The most primitive hole challenge is cleaning the hole, which is more severe in deviated wells. This problem was tackled in this research via experimental analysis and graphical evaluations. To hit this aim, rheological parameters were experimentally obtained, and Noah’s model was used to determine cutting bed erosion time at varying heights. A graphical evaluation was done using a case study of deviated wells X and Y from a Niger Delta field. The result shows that low-viscosity fluid, KCL polymer fluid and high-viscosity fluid take 124, 283 and 342 min, respectively, to erode equal height as graphical evaluation shows that hole cleaning will grow complex on deviation. Thus, the deduction from this work in reducing non-productive time (NPT) related to hole cleaning in drilling operation is first, prior to making a trip, pumping low-viscosity fluid at a high flow rate. Secondly, during drilling, increasing drill string rotation in deviated wells can effectively stir the cuttings into the annulus above the low session of the hole.

Modeling research on the extreme hydraulic extension length of horizontal well: impact of formation properties, drilling bit and cutting parameters

Horizontal well can increase well productivity and improve the economic benefit, which significantly promotes the development of shale gas, tight oil and heavy oil. Moreover, it plays an important role in the development of natural gas hydrate. Horizontal extension ability is one of the key indexes of horizontal well, but it is always impacted by formation properties and well structure. Therefore, a model is established to analyze the impact of formation properties and well structure as comprehensive as possible, which considers not only traditional influencing factors, like formation pressure and drilling bit parameters, but also other key factors, including cutting particle size, wellbore diameter and cross section. Based on the analysis, some advises are proposed for field application. The analysis indicates that horizontal well has stronger extension ability in the formation with low formation pressure and high fracture pressure, but it is still limited by pump pressure. Under-balanced drilling can strength the extension ability in high formation pressure by reducing drilling mud density. The natural fractures in formation should be noted when drilling long horizontal well. The extension length increases and then decreases with the cutting particle size, so cutting particle has optimal size for the horizontal extension length, which can be adjusted by the rate of penetration and rotation speed. The extension length increases first and then decreases with the gap between drilling string and hole. Considering the demand of rock breaking and cutting sweeping around drilling bit, it is not recommended to adjust the drilling bit parameters. Both the cutting bed height and drilling string eccentricity have impact on horizontal extension length by changing minimum cutting-carry pump rate and annular pressure drop. Under different combinations of above two parameters, minimum cutting-carry pump rate and horizontal extension length are determined by different factors and can be divided into three parts, including acceptable cutting bed height, cutting lifting efficiency, pump pressure and total circulation pressure loss and well bottom pressure and formation fracture pressure. The findings of this study can help for better understanding of horizontal well hydraulic extension length and optimization method.

Effect of Near Wall Turbulence on the Particle Removal From Bed Deposits in Horizontal Wells

Although solids entrainment and deposition mechanisms have been studied extensively over the years, our understanding of fluids-particle interactions near bed interface is still limited. Progress toward such understanding has been relatively slow because of the difficulties inherent simultaneous measurement of local solids transport and adjacent near-bed fluid flow. With the introduction of non-intrusive measurement techniques such as Particle Image Velocimetry (PIV), it is now possible to determine the instantaneous velocity field and observe particle deposition/resuspension simultaneously under non-uniform flow conditions. An experimental program was conducted to investigate different aspects of turbulent flow of water over the cuttings bed deposited in horizontal annuli. A large-scale horizontal flow loop consisting of 9 m long high quality optic glass pipes (95 mm ID of outer pipe and 38 mm OD of inner pipe) equipped with state of the art PIV system has been used for the experiments. Turbulent flow over cuttings bed experiments were conducted at superficial Reynolds numbers of 9300 and 10800. Natural irregular shaped quartz sands with 3 different mean sieve sizes of 260, 350 and 600 micron were used as solid particles. The proposed work was accomplished through several tasks: i-) conduct experiments to measure the instantaneous local velocity profile during turbulent flow in the horizontal concentric annuli and examine the effect of stationary cutting bed on the local velocity profile, Reynolds stress and turbulence intensity; ii-) investigate the impact of particle size on the near-wall turbulent activities. Results have indicated that existence of a cuttings bed on the lower side of the wellbore dramatically alters the near wall velocity profile comparing to the case with no cuttings bed. Presence of cuttings bed causes the maximum velocity to shift toward the inner pipe. Presence of stationary cutting bed causes a reduction in Reynolds stress, axial and radial turbulence intensity, which in turn, would adversely affect the hole cleaning. Larger cuttings slightly enhanced turbulent stress and radial intensities. However, the increase in these entities as a result of increasing cutting size was far less than the decrease in them as a consequence of presence of stationary cutting bed. Axial turbulence intensity was the same in the core flow away from the cuttings bed for flow with and without a cuttings bed. However, the peak of axial intensities is shown to be less for flow near the cuttings bed.

Dimensional Characterization of Surface Contours of Cut Surfaces with Plasma Straight Metallic Materials

The purpose of this paper is to analyze the dimensional accuracy of the surfaces straight edges from cutting plasma free atmosphere or water bed. The aim was to identify any defects and if bed piss water cut in some way influence the surface quality and dimensional contours right. Mechanical thermal plasma cutting bed prevents overheating of the water has the advantage that the base material and thus the parameters related to compliance with the slag assures cut pieces at the bottom, this saves the cost of production. Mechanized plasma cutting bed heat the water does not affect the value of angle tolerance compared to cutting outdoor (angular deviation determined either for parts or cut outdoor water bed ranged between 7-9 degrees / side). The causes of and ways to reduce the deviation angle cut edge is determined by other factors such as cutting speed, distance torch-material, cutting nozzle erosion.