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        Engineering Technology R&D

        Based on construction practices and experiences, Huayuan developed such innovative construction techniques as drill-bits handshake intersection and power-reamer borehole opening. These  techniques can fulfill various construction requirements under different construction environments.

        1、Drill Bits Handshake Intersection 

        This technique of drill bits handshake  intersection developed by Huayuan, is mainly used in pilot hole drilling with long distances, in such complex ground strata as soft formation, soft & hard alternative formations.

        When the pilot hole is drilled by using two drill bits from both ends simultaneously to the intersecting midway, upon approaching the anticipated intersecting range, the instruments mounted behind the drill bits will be started for down hole surveying (guiding) and intersection. One drill bit will receive the signals sent by the other. After the signal data being collected, calculated, and the relative positions of the two drill bits are ascertained, it will be started to steer the two drill bits to the proposed intersecting orientation according to the calculated results, finally the two drill bits can intersect and couple together (handshake). At last, the coupled drill strings (becoming one single drill string) will be withdrawn from one end, thus a continuous pilot hole is successfully completed. 

        Actual Application: Waidiao Island – Cezi Island Offshore Pipeline HDD Crossing Project; Yellow River HDD Crossing Project for Boai-Zhengzhou-Xuedian Gas pipeline, etc..

        2、Borehole Reaming With Two Rigs

        When crossing rock strata of high hardness and high abrasiveness, besides appropriate down hole tools should be selected and used, the technique of Borehole Reaming with two sets of Rigs can be applied. This technique can improve reaming productivity, reduce such risks as jamming or breaking of the drill tools, and accommodate extensive range of various properties of drilling fluid. At present, the Borehole Reaming technique simultaneously using two Rigs is vastly used in our projects construction. 

        Actual Application: Yellow River HDD Crossing for the Shandong-Anhui Product Oil Pipeline (the 2nd Phrase), etc..

        3、Pilot Hole Intersection Technique

        When pilot hole drilling, if the length is reaching more than 2000 m, it will be very hard to satisfactorily steer the drill bit underground. In addition, if steel casings are installed at both ends of the entry point and daylight point, the steel casing will disturb the magnetic fields for drill bit positioning, causing it nearly impossible to steer the drill bit accurately entering the casing on the opposite side.

        Huayuan developed our own intersection technique for pilot hole drilling, which need to deploy two sets of rigs on both the entry site and the daylight site respectively, drilling the pilot hole from two ends simultaneously, until intersecting at the midway. This method can properly resolve the construction  difficulties above mentioned. Moreover, this intersection technique can avoid the problem of Lost Circulation of drilling fluid, and can reduce the risk of mud flee to the ground due to high mud pressure .

        Actual Application: Yangtze River HDD Work for Jingzhou-Shishou Gas Pipeline; Yellow River HDD Works for Anyang-Luoyang Gas Pipeline, etc..

        4、Mud Power Reaming Technique (forward and backward)

        When reaming for very long a distance by using traditional reaming technique (rig driven), unduly torques exerted on the drill string is actually a kind of power waste and a risk. Huayuan developed our own mud power reaming technique, to use the pressurized mud for driving the reamer, when the powers are transmitted to the cutters of the reamer directly. This technique can increase the reaming productivity, and decrease the wear rate of the drill pipes. Reaming rate in rock formation can be increased by this technique up to 3~5 times.

        Actual Application: Huanggang-Daye Yangtze River HDD Crossing (Gas Main), etc..

        5、Thrusting Installation of Pipeline

        On the constraints of the HDD working site, pipeline will be installed by using thrusting technique, instead of back pulling, when the pipeline thruster mounted on the drill rig can thrust the pipeline into the borehole. This technique is usually used combined with the forward reaming technique, when the pipeline prefabrication area will be designated at the drill rig site.

        Actual Application: Chonagqing-Qijiang Yangtze river HDD Crossing (Product Oil Pipeline), etc..

        6、Assistant Pipeline Back Pulling

        When large resistance is encountered during pipeline back pulling, the assistant thrusting device will be used at pipeline entering end, i.e. the pipeline prefabrication site, so as to alleviate  the pulling force of the rig and the drill pipe.

        Actual Application: Yellow River HDD Crossing. Boai-Zhengzhou-Xuedian. Natural Gas Pipeline Construction, etc..

        7、Pipe Jacking in Cobble Layer

        When HDD drilling through cobble layer, steel casing will be firstly jacked through the whole layer of the cobbles, to protect the drilling activities by sealing out the cobbles. 

        Actual Application: Yellow River HDD Crossing Project for Luoyang-zhumadian Product oil Pipeline Construction, etc..

        8、Bore-wall Supporting in Cobble Layer

        If the grain size of the cobblers is no more than 50 mm, meanwhile the constituent of cobbles in the formation layer is no more than 50%, specific mud will be used to support the bore walls.

        Actual Application: Yangtze River HDD Crossing. Jingzhou-Shishou. Natural Gas Pipeline Construction Project, etc..

        9、Borehole Gauging and Simulated Back Pulling

        The borehole can be gauged and pipeline back pulling can be simulated by using the professional software developed by Huayuan, so as to ascertain the attributes of smooth-going of the borehole before actual back pulling.

        Actual Application: Huanggang-Daye Yangtze River HDD Crossing (Gas Main), etc..


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