Sand production during the course of hydrocarbon production is a common phenomenon. However high sand production with its attendant damaging effects on both downhole and surface accessories have led to an increasing demand for both down hole and surface sand control in the oil and gas industry.
Sand production in Clientfield has led to loss of revenue due to reduction of well choke, increasing pigging rates, reduced pumps efficiency, maintenance cost and frequent de-sanding. Currently, the spot sampling technique for determining sand production is inadequate and adversely impacts decisions on field management.
The common approach to sand monitoring has been monthly surface sampling and laboratory analysis. Challenges surrounding monthly sampling are long interval between each sampling and testing, spot sampling not representative in a continuous flow fluids system with varying velocity and sand content, poor repeatability of test result and in many cases results could be highly optimistic – given false high sand alarm to operators.
Oil and gas well operators know how important it is to maintain production at optimum levels, and an important part of that optimisation is a clear and accurate measurement of solids production. The SandAlert range provides robust, dependable measurement of solids within the production stream, so you can be confident that you are operating as efficiently as possible. The SandAlert system consists of two parts: The PulsarGuard 2001 sensor, a small, robust clamp-on acoustic monitor, and the SandAlert controller. SandAlert is ideal wherever you need to keep wells producing efficiently at the highest rate possible. The unique PulsarGuard sensor is installed after a suitable pipe bend where the turbulent flow profile is fully developed. The sensor measures solids production directly, without the need for an external or additional flow measurement
Equipment
Functional Description
The high frequency structure borne acoustic signal generated by a sand impact on the internal wall of a pipe, travels through the pipe wall and is detected by the acoustic sensor. The acoustic signal is then converted to an electrical signal by the sensor.
The electrical signal or sensor output is processed by the electronics in the SandAlert Portable control unit to provide a sand impact rate (SIR) in impacts per second (IPS). (This figure is then used by the calibration algorithm to give sand mass).
To illustrate this the following figures (a,b,c & d) show the types of signals that you would expect under conditions of high and low flow rates, with and without sand impacts:
1. Equipment Installation Procedures
Site Visit
Sites visit involving Contractor’s personnel and CLIENT focal point (s) on the operation and would be
Conducted prior to mobilization to ascertain the following:
- Accessibility to w/head or point of installation
- Availability of a suitable angle 90 degree bend for each installation
- Affirm availability of a safe area where the sand monitoring on the PC laptop would be ongoing
- Measure the distance from the point of sensor installation to the safe area to provide adequate length of cable
- Check and verify integrity of swab and w/head needle valves
- Availability of an ½” NPT male connection
- Identify source of portable water
- Community issues; negotiation and settlement
Installation Procedure of Sand Probes
Mounting of Sensor:
Sensor is mounted downstream of a bend point (bend, elbow, tee) in the line and located on the outside of the corner.
Attachment:
The sand detector sensing head is attached to the pipe by screwing it into a unit (skid) which has been clamped to the pipe using metal straps. Once installed, the base unit will not need to be removed except if the signal is noticed to be weak and unreliable. The most likely cause of an unusual decline in signal is poor contact between the pipe surface and the sensor head. Silicone grease is used to ensure good ultrasonic contact between the sensing head and the surface of the pipe.
Surface preparation:
Since the acoustic sensor picks up the energy from the particles impacting on the inside of the pipe, it is important to obtain the best possible acoustical contact between the sensor and the surface of the pipe. Therefore paint and other coating on the pipe surface must be removed. A circular spot should be smoothed, cleaned and treated with silicone compound to improve the contact between the sensor and the pipe surface. This is usually done via the following steps:
Remove paint and coating with a knife or file in a marked circular spot. The sensor probe head has a diameter of 8mm, but it is recommended to prepare a circle of minimum 2 cm in diameter.
Use a file to remove any roughness in the pipe surface.
Rub the spot with sand paper to achieve an effectively smooth area
Clean the spot with a smooth cloth –moisten with grease dissolving fluid.
Note; Silicone compound must be applied prior to sensor installation
Mounting Of Skid:
The stainless steel clamping bands for the skid are delivered in1 meter lengths each if not otherwise specified. This is sufficient for an outer pipe diameter of DN 640 (25”). If the particle monitor is going to be permanently, the bands should be cut to fit the actual installation.
Fit the band to the actual installation. Make sure you are using one band with a threaded part and one without a threaded part. You might be able to stretch the bands while tightening them.
Fasten the bands to the skid with the m6 screws through a hole in the band.
Hand tight the fastening screw.
Check that the skid is sufficient fastened, and that you are not able to move the skid by hand.
Mounting Unit
The particle monitor is easily installed in the skid by screwing the whole unit 4-5 rotations until there is metal to metal contact between sensor probe and the pipe.
Check that the particle monitor is free of fault and the sensor and the threads are clean
Check that the skid is securely fastened
Clean with smooth cloth and moisten with grease dissolving fluid
Apply silicone compound
Screw the unit into the skid and hand tight with both hands
Tighten the fastening screw on the clamping band ½ turns
Tighten the 2 screws on the skid
Verification of Installation
To make sure the particle monitor is correctly installed and securely fastened, the following checks are performed .If any errors found, the installation is incorrect and reinstallation should be done according to procedure.
Try to move the unit by hand –this should not be possible.
Try to screw the unit further into the skid – this should not be possible
Make sure that the particle monitor has metal-to-metal contact with the pipe structure for earthen purposes.
Power Requirements
The portable ClampOn particle monitoring system consists of the sensor, 100m twisted pair cables and the power supply unit (PSU). The PSU powers the sensor with 2 watts (15 watts at start up) and is itself powered by 110-230Vac. the sensor is EExia certified but the PSU is not and hence has to be kept in a safe area.
2. Reporting Format:
A daily report shall be submitted to the CLIENT representative at end of the 12-hr daylight operation. Sand measurement basically would be reported in two ways:
- Qualitatively: establishing the highest sand free-limit
- Quantitative: sand rate (density) in PPTB; grams/sec (g/s), Total sand in pounds (Lb)
3.Onsite procedures
- Hold safety meeting with all the personnel involved and discuss objectives, procedures and exit routes.
- Layout equipment as per figure-1.
- Install the sensor at the identified suitable bend –
figure 2.
Figure-1,2 – elbow connection for effective particle detection
- Start the Clamp-On sand monitoring by lining up interval to test separator (if no result test data)
- Start-up monitoring software and monitor the signal for at least one hour to identify good or bad patterns.
- When flow is observed stablised, collect surface sample for immediate laboratory analysis (if no recent lab sand data).
- Produce wells with flowline less than 1KM for 4 hours and wells with flowline longer than 1Km or gas lifted for minimum of 6hours to ensure proper well stability and data repeatability.
- Download data to analyze using the ClampOn software for the period logged.
- Extract logged data and calculate sand impact and rate for the period logged.
- After the baseline ultrasonic sand monitoring, if sand production is less the 10ppt, the well will be ramped-up and re-tested. Otherwise, the well will be choked back and re-tested at CLIENT instruction.
- Process of optimisation will continue until an optimum oil rate with sand rate less than 10pptb is obtained.
Case History New Oil and Gas Well– Ramp-up
