DESCRIPTION OF CUTTINGS TRANSPORT TEST FACILITY AT TUDRP
The major part of this spring’98 work is the modifications of the existing wellbore simulator (Schematic representation of the whole flow-loop is shown at the end of this section), that will allow experimentalists to carry out full-scale research in two major areas related to the petroleum industry:
The main design objectives of this test facility are as follows:
In order to meet the above requirements the existing full-scale flow loop system was modified.
The main flow loop components from cuttings transport point of view consists of the following:
Each of the above system components is briefly explained below
The test section is an 8" transparent acrylic pipe with a 4 1/2" rotating drillpipe inside, creating a 100’ long annulus. However, test section of up to 12 1/4" steel casing with corresponding drill pipe can be used. The test section, which will be referred to also as the wellbore, rests on a rigid box-beam steel structure. The box-beam (or support frame) is composed of two Vulcraft steel joists (48LH special Joists), positioned 3 ft apart, and laterally braced in multiple directions. It is designed such that an insignificant amount of deflections will be experienced when fully loaded. The support frame also contains two sets of four field-bolted splices at the middle of the test section. This will allow the mid-section of the frame to be taken out and or modified to accommodate any wellbore size, such as wash outs. A very important characteristic is that approximately 70’ of the test section is transparent. This will allow investigators to identify cuttings transport patterns and conduct their tests more effectively. The pipe consists of fourteen 6ft and one 2ft long acrylic pipes held in position with STRAUB couplings of ½ in. wall thickness. The couplings allow for some degree of flexibility both in axial and lateral directions and there by reducing the possibility of breakage of the acrylic pipe. The pipe sections are clamped to (rubber-padded) saddle seats. The seats are bolted to a position inside short pieces of rectangular tubing that are welded to the center of the top cross-braces on the support-frame.
The bottom end of the test section is connected to a 6" metal flexihose which in turn
is connected to the cuttings outlet of the cuttings injection tank (hopper). The top end of the test section consists of 180o U-turn. This is flanged (with a Dixon ‘V’ ring type swivel joint, style 40) to a green 6" flexible PVC hose (sectioned in 10ft lengths and connected with quick couplings). The green hose is flanged to 6" pipe (with a Dixon 6" swivel joint, style 30) that leads to the flow of solids and liquid from the wellbore exit into a small catch basin in a remanufactured PetroQuip single tandem shale shaker. The slurry overflows from the basin onto two screens (20 mesh and 40 mesh), where separation of solids and liquids takes place.
A cuttings injection tank (hopper) and cuttings collection tank (cuttings chamber) make up the solids handling system. They are cylindrical tanks with step-broken bottom cones. The hopper (manufactured of 1/8" high strength rolled steel) also has a top cone with a center bolted lid. Similarly, the cuttings chamber is made of 3/16" high strength steel with an offset top cone with a bolted lid. Both tanks have bolted manholes on the sides. The open bottom cone of the hopper is welded to a pipe where the auger screw conveyor is inserted. The bottom of the cuttings chamber is flanged to a pipe with internal nozzle (a standard 2X4 concentric reducer) to enable the cuttings flush-back process to take place effectively. Inside the 10", 300# slip-on flanges, a circular ¼" steel plate with a 3.5" diameter center hole is positioned to control the flow of cuttings from the collection tank to the jetted flow of liquid in the pipe underneath. Several similar replacement plates with varying hole sizes are made up in case gelling should turn out to be a problem in the cuttings chamber.
The cuttings are injected into the annular test section where the cuttings merge with the main mudflow, which is accomplished by:
One load cell, which is mechanically operated, is fixed to the top section of the injection tank, in order to continuously monitor the total weight of the assembly and its contents. A Dominator 738 is used to monitor the weight as test progresses from start to end; the cuttings level in this tank is being decreased from full to empty. The injected cuttings are automatically replaced with liquid to maintain a full hopper. Consequently the actual cuttings injection rate can be found by simple equations:
From actual cuttings injection rate to rate of penetration:
From monitored cuttings injection rate (MCIR) to actual injection rate:
The main components of the rotary system are a 4.5" O.D hard PVC drill pipe and a rotary drive motor assembly. One of TUDRP’s most important contributions to the industry was a study of the effect of drillpipe rotation. Unlike previous, the drillpipe was not constrained with centralizers, rather it was allowed to rotate freely. As a result, the drillpipe had rotation around its own axis as well as orbital motion. Contrary to what had been published before, the reduction in cuttings concentration as a result of drillpipe rotation was significant. Since it is believed that this motion is close to what occurs in the field, most cuttings transport studies that involve drillpipe rotation are conducted without centralizers. The drill pipe is held at either ends by stabilizers/centralizers with built in bearings between the outer pipe flanges. The drillpipe can be rotated from 0 to approximately 200 rpm, and its position can be changed to vary the annular eccentricity by externally adjusting the centralizer holders at the extreme ends. The motor is a 5hp (1750 rpm, 480 V, 3-phase) electric motor with a variable-speed drive unit (Vector V437E3). The motor is attached to a 90 degrees gearbox (1:10 reduction ratio). The output torque from the gearbox is transferred to the drillpipe, through the U-turn of the annulus exit. An O-ring sealed moveable base plate allows annulus eccentricity adjustment for the drill pipe sections near the exit, and an aluminum bearing housing prevents occurrence of leaks in the transition between wet and dry environment. A Himmelstein torque-meter with low velocity speed pick up option is used to monitor the drillpipe torque and rotary speed.
The hoisting system consists of a drilling line (7/8" diameter steel rope), crown block that sits on a top of a derrick structure, a vertical lead sheave mounted to the top end of the support frame (functions like a fixed one-sheave travelling block) and the draw work. The drilling line dead end is connected at the top backside of the derrick. It is shackled with two ¾" wire slings to lugs, which are welded to one of the main horizontal derrick beams. The line then is strung between the lead sheave and the center sheave in the crown block. The fast line goes through a McKissick Champion snatch block with shakle (8" sheave size), before going into the drum of a Tulsa Winch model 64. The snatch block is shackled to a universal tension force sensor (Transducer Techniques load cell; SW-30K) via two custom made male crevices . The tension load cell is bolted to two-fixed derrick lugs. The hook-load indicator monitors the total weight of the support frame with test section and all inside contents. The winch has an automatic worm brake with a mechanical drum brake, which is engaged by a Speedaire air cylinder and can be remotely activated. The winch is powered by an Eaton ME 300 low speed torque hydraulic motor, which again is powered by a custom-made hydraulic power unit with an Eaton series 33 pump with electronic stroke control. Operation of the hoisting system takes place from the control room using a panel mount electronic control lever. Remote start of hydraulic power unit and alarm indicators is also sited in the control room.
Mudflow control is done with fisher control valve (this system is governed by programmable logic controller, PLC) and a constant speed Centrifugal pump. It is a user operated via the Loop Access Mode (LAM) unit in the control room. Accurate flow rate monitoring is provided by a Micro Motion mass flow meter. Its panel indicators also display fluid density and flow temperature in selectable units. Exiting the flow meter, the fluid can be diverted into two ways: towards the annulus inlet for normal drilling simulation, or through the cuttings chamber for transporting cuttings back to the hopper.
One of the many attempts at making this flow loop system highly efficient resulted in the development of a hydraulic conveying system for transporting cuttings from the collection tank to the hopper. The system uses the mud as the transporting fluid with the mud pump as the driver. After the hopper is drained for cuttings, testing has to be temporarily stopped since all the cuttings now sit in the cuttings chamber. To refill the hopper, the cuttings are hydraulically conveyed from the cuttings chamber back to the hopper so drilling simulation can resume.
A 100-bbl open mud tank with high power agitator is used to provide storage for the liquid and a 4ft head for mud pump suction during circulation. The total mud tank structure is divided into four parts:
Manual valves provide drainage of all tanks. Floor grating with toe-plates, double railing and ladders enable safe walking on top of tank system. The tanks are roofed using R-panel galvanized siding. The shale shaker is positioned above the settling tank and under the roof at a height that ensures natural flow of solids from the shaker into the collection tank, which is positioned on an extension of the mud tank foot base.
The field signals are carried to the control room via appropriate twisted and shielded cables in one of two ways. The first cable way is designated for high-voltages lines (110-480 V). The second cable way is for low voltage incoming field signals where high accuracy is desirable. The cable may merge outside the control room before the cables enter their respective panel indicator. As described above, two Dominator 738s are used for displaying weight of the cuttings collection and injection tanks. These panel indicators perform functions like gross, net, tare, zero, print, unit conversion, and use of time/date and ID number. Analog output options from these indicators make connection to a data acquisition panel convenient. Similarly, the two mass flow meter indicators provide readings of mass rate or flow rate (Digital Rate Totalizer), and fluid density and temperature (Density Monitoring System) with corresponding analog analog signal outputs. The drillpipe rotary speed and torque are displaced by use of a Himmelstein torque and speed readout device (No.: 66300).
Chessel Model 750 Process Monitor/ Indicator panel meters was used for readouts of pressure, temperature and hook load. The indicators for winch body temperature, hook load and air supply pressure can effectively be utilized in conjunction with the PLC and a programmable message display (PMD) for the shutdown systems. Selectable automatic (by use of the PLC) or manual operation of the following components is possible by operating manual/automatic switches (not to be confused with PLC loop access module mode):
In addition, the switch operation is manual, where all the above components are operated by their respective switches and potentiometers. Switch (on/off) operation of the following accessory equipment is possible:
A Texas Instrument PM 550 programmable logic controller (PLC) is employed to govern all process control of facility operations. User operation of the PLC takes place with the loop access module (LAM). The following loops are assigned:
Loop 1: Mud pump speed control (in conjunction with the Teknar controller)
Loop 2: ROP control (by Hydraulic system which has 4-20 mA controller)
Loop 3: Drill pipe rotary speed (works accurate enough manually)
Loop 5: Immersion heater with a SCR controller
Effective use of the PLC capabilities has an impact on safety and to what degree automation is achievable. Some process control can be achieved using the options in the data acquisition system via output channels.
In conjunction with the PLC a programmable message display (PMD) can be used. The Uticor PMD 200 is an intelligent, alphanumeric display panel, which can be programmed with individualized messages. The PMD can be used to provide information on process diagnosis, operator promoting and fault indicators. It can interface with any type of controller and printer and it can be programmed using the PC with an RS-232C interface with software for terminal mode.
The complete data acquisition system consists of the following components positioned on a designated table next to the control panel:
The data acquisition board is an analog/digital, input/output that is plugged into one of the expansion slots in the PC. Strawberry tree terminal board supports the direct connection of 16 single ended high-level analog input signals. This panel is a daisy chained to the STB-TC screw termination panel that supports the direct connection of 16 low-level differential analog input signals.
In terms of software, LabTech Control (LTC) version 3.2 with ICON view (graphical interface that lets the operator create data acquisition and control setups by moving and connecting icons by using a Logitech Series 9 serial mouse) is used. A PC paintbrush free-hand graphics paint program is also part of the LTC.
The LTC program has the following main features:
Alarm monitoring and control
Real time data display
Data logging and storage
LTC can monitor and record the following types of process variables:
Voltage, current, temperature, strain, displacement, discrete (on/off) points
Variables can be defined through input or output function blocks, which can be scaled
and displayed in engineering units. Definitions of derived blocks for time, replay and
calculation purposes can also be used.
A Panasonic CCTV system is used for visual flow observation and recording purposes. In addition, the remotely operated camera system can also assist in area surveillance when crucial operational steps take place. A WV-LZ81/6 zoom lens and a ½" WV-CL704 (24 VDC) high resolution CCD color camera is used inside an outdoor housing: WV-7160. The weatherproof housing is equipped with heater, fan, defroster and sun shield. The housing unit sits on top of a heavy-duty outdoor WV-7260D pan/tilt mechanism. This device enables the camera to pan on an angle from 10-340 degrees at a speed of 3.6 degrees/second. This unit is mounted directly on a square flat plate which is a part of a mechanical system that ensure that the camera system base is always positioned horizontally regardless of support frame inclination angle. This video camera platform is moveable and can be clamped in any position along the test section. Two control units control the video system. The WV-7360 controller provides remote control of the housing and the pan-tilt mechanism. The WV-CU204 system controller enables remote control of the various camera functions. A CT-1381Y 13" diagonal color video monitor is used to convey the picture of interest to the control room operators.
A centrally located control room houses instruments for monitoring the total system.
A control panel for remote operation of valve positions, hoisting system, mud pump, communications system and other accessories are located in the control room. The 18ft X 11ft air-conditioned control room has three tinted windows in the front for maximum operator visibility in all directions. The control room is positioned in front of the mud tank body for easy detection of potential irregularities during circulation. The annular test section can also be well observed from the control room. A paging system and use of walkie-talkies enables communication with personnel outside. Fluorescent panel indicator displays and multiple floodlights strategically placed around the TUDRP facility enable operation after sunset.
A new Pentium computer of National Instruments hardware & software (Labview) is bought. The existing system will be replaced with the new computer.
To ensure compliance with normal safety and environmental standards, a number of design features are incorporated in the facility design:
---Temperature of hydraulic power unit for hoisting system
---Fluid level in hydraulic power unit