Engineering example

1 engineering general situation of a project is located in the northwest of pingdingshan, channel for the silty soil layers, the upper clay for 2-3 m, lower level of silt. Underground water level is low, the pipeline horizontally across the river total length of 560 meters, pipe composite pipe of 355 mm diameter.

2 construction design 1) guidance trajectory design basic parameters meet the specification requirements of the minimum curvature radius, R = 1500 dn = 750 m, because this project through the strata are mainly fine sand, gravel, clay, the difference of formation pore forming, poor stability, in order to reduce the bending stress of the pipeline, increase cross section through the radius of curvature of the pipeline to R = 2000 dn, R = 960 m.2) drilling Angle and radius of curvature in most through the construction of the grave Angle usually choose between 8 to 12 degrees, most of the construction should first drill a diagonal line, then drill a larger radius curve. The radius of curvature of curve is determined by the finished product pipeline bending properties, along with the increases IN diameter, steel tube radius of curvature of the thumb rule is 100 ft/IN (usually take 1000-1200 times the diameter of the pipe).Skew lines will guide hole curve according to guide to the design depth of the book, and then is a depth on this long straight and level, and then reach upward bending points to unearthed.The unearthed Angle should be controlled between 5 to 12 degrees, so that the finished products pipeline back to drag.3) through parameter design through parameter design are shown in table 1.4) drilling construction assembly table assembly of the engineering construction are shown in table 2.3.3 slurry preparation according to the geological data, determine the slurry preparation plan, the implementation of mud drilling, drilling in good preparation before 30 square mud with high quality.Mud plays a key role in directional crossing, we will adopt different according to different formation of mud, if the complex geological conditions, the requirements for the mud is higher, in order to deal with different situations, we will take the following measures: 1) according to the pre-determined ratio of slurry with good level of bentonite and mud additives, and meets the requirements of the mud.2) use of mud additives are: polymer HFEC, DFD – 140 fluid loss agent, lubricant, according to the different through geological conditions, determined to join different additives.3) in order to guarantee that the performance of the slurry, bentonite has enough hydration time, in the case of dosage can’t change, will be taken to increase the number of the mud tank.4) of waste mud treatment: dig a waste pulp in welding field collection pool, collecting waste mud, after precipitation treatment; In the drill ground also dig a mud recycling pool, mud after precipitation recycling pool, again through the mud recovery system recovery; Recycling is not the mud to the designated place.

4 pipeline towing guide hole back after grading pre expansion, hole cleaning, aperture to pipeline back to drag the required conditions, will test qualified through the pipeline on the skid frame and check after being dragged back. Is dragged back through the last step, also is the most crucial step, in the back to the way of construction is adopted in tow: Φ reamer 650 + 40 t drag swivel back + Dn500 crossline (Dn500 is 3 x + 1 x phi phi 250 MPP line 75 MPP line).When back to drag for continuous operation, to avoid sticking due to shutdown. Drag on the careful inspection of the rotating joint connection, connection head, reamer, determine the connection is firm may drag back, back to drag on both sides to strengthen the contact, coordination will be pipeline installation to the desired location.

5 1) pipeline protection pipeline back pulling the front line of prefabricated completed acceptance, acceptance of content: the quality of pipeline is unqualified, whether carried out in accordance with the design requirements for all line decoration, is in line with the pipe ovality, pull head do whether qualified, confirm qualified rear can back to party a notice.2) pipeline before must back to inspect, pipeline found peel off, replace pipe deformation and other issues must inform party a, in order to drag in unnecessary trouble and bring unnecessary economic loss to party a delay time into society to bring economic benefits.3) the last bore hole to improve the lubrication performance of mud, the last time back to drag to keep expanding the mud property, avoid significant adjustments to mud caused by the collapse of hole wall, add resistance to pulling.4) both ends of pipeline to drag must be checked before closed situation, pipeline back in place after the remained sealed on both ends of the line, make sure the line clean.5) pipeline back to drag process must have the specialist is responsible for the patrol inspection, leakproof personnel on-site promptly leakproof.

6, quality assurance measures are 1) the measures to prevent it is “S” type while drilling directional device adopts the DCI MARKIV positioning equipment, strictly control the whole Angle in the process of directional drilling rate, shorten the measured interval length as far as possible, especially in formation change or gravel, hard and soft parameter measurement spacing shall not be more than 2 meters. Adjust bearing in a timely manner, and have margin, banned repeatedly greatly adjust Angle, to prevent the “S” type.2) ensure that measures within the scope of directional drilling out the error in the design of a rig measurement is in place, using total station accurately release the centerline of the drill in place;The second point to parameters, accurate measurement calibration requirements carefully and as much as possible acquisition parameters comparison, to determine the best parameters, three different position at the center line of acquisition, and each location at least four times, and make records.3) to ensure smooth the reaming measures has been the guide hole, must meet the requirements of pipeline radius of curvature, especially not in “S” type curve;Second, according to different formation timely adjust mud, the cross section of formation is relatively complex, timely adjust the mud proportioning according to different stratum, appropriate control mud viscosity, increased fluid loss agent, lubricant and prevent collapse agent added amount, to stabilize the hole wall, reduce shrinkage, stable mud property, prevent significant adjustments to the mud, and cause the collapse of hole wall.4) measures to ensure the success of the back drag at the scene we prepare two electric hoist, to ensure the smoothly back to drag.4, the conclusion due to the complexity of the project for big diameter formation crossing, cross the strata are mainly fine sand, gravel, clay, the difference of formation pore forming, poor stability, the guide hole drilling, the thrust is bigger, request to anchor must be strong, mud performance to achieve high viscosity, good flow, appropriately increase the pump pressure, improve hydraulic horsepower.

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