an essay concerning subsea pipelines flexible api 17j 20150809

the knowledge, expertise and knowledge are generated in dongfang 1-1 gasfield, phase 1 development/adjustment wells project, water depth 70 meters around, the flexible pipelines were fabricated in a yard near the coastline in wudi, binzhou, shandong, china and the pipelay vessel alongside the coastline as well.

to understand subsea flexible pipelines, the following points are to be addressed:
  • fabrication
  • composition
  • functionality/application
  • installation
  • commissioning
  • operation (workflow, or the service process) , start-up
  • maintenance (rov/cctv, or as george orwell called ‘big bother’ whatever you name it)
  • after-sales service (spare parts, facility statues inspection and that sort of things)
subsea flexible pipelines (API 17J &B) generally consist of these layers, each may or may not be subdivided:
  • carcass
  • inner sheath/liner
  • pressure armour
  • tensile armour
  • external sheath/liner

interlocked carcass

it is metal and the wellstream is supposed to travel within the carcass

inner sheath/liner
it is extruded from unbonded polymer, it seals the liquid leakage in the annular betwixt the two armors, and prevents the carcass from the corrosion caused by liquid leakage in the annular in the two armors

pressure armour

it is supposed to be pressure-resistant, but i have no idea whether it is the inner pressure of the wellstream in the carcass or the external pressure from the currents or waves in the waters… it has 4/6 sublayers. it serves with the function of preventing the carcass from the collapse caused by pressure.
tensile armour
it is resistant to tensions despite the flexible pipelines are burial, but if the pipelines are not buried beneath the mudline, it flows on the sea floor, then it screws, and thus the torques/tensions (clockwise and anticlockwise) are created, the tensile armor that consists two sublayers is resistant to the each direction of tensions
outer sheath/liner
extruded from unbonded polymer as well, it is fabricated from the same machine that the inner liner comes out from. the function of this layer is to seal the liquid leakage in the annular in the armors together with the inner liner, and seals the pipelines from sea water.
hydrostatic testing was performed, i didn’t come close because i might be hurt due to the high pressure, the testing lasted for a long time.
with the pipelines were fabricated and tests performed, they were transported from the yard to a pipelaying vessel, i saw a tensioner was used. the pipelines were placed in a basket on that vessel rather than a reel – i assume it is not reel lay – because it was in a basket.
an anti-wear tap layer was included sometimes. i believe a sensor is supposed to be attached to one layer to detect the fatique, durability and leakage things, but we didnt have it as we just started to develop it year ago. we have to bridge the gap with whatever the effort we must make, and with each feature of the innovation gathered and united in a product, we must penetrate inch by inch alongside the predesigned course to meet the target.
the experience was fruitful and worthwhile despite it was near the shore/shine/coastline and 40 miles far from the county.
with composition and the functionality of each layer and sublayer explained. we now come to the the flexible pipelines applications.
subsea pipelines serve in the production phase and midsteam (gathering, transportation and storage).
generally the offshore wells are drilled as satellite or cluster wells.
as for the cluster wells, a template is installed on the seabed with some holes in it – 6, 8, it depends. and the drilling is conducted through the holes. the wells are close to each other, but beneath the mudline they are deviated. but satellite wells are individually drilled and connected with flowlines(flowlines can also be rigid) to manifolds, and manifolds connected with riser base so that the production, injection and export become a possibility. the flexible pipelines applications are:
  • production pipelines, transporting the wellstream to an offshore platform or onshore facility
  • injection pipelines (of chemicals, additives, water and gas) to lift the oil from the payzone for recovery
  • export pipelines, after the wellstream treated and processed on the platform with three phase separator that separates oil, water and gas, then the oil, if not exported to shuttle tanks though floating hoses, is sent back through an export riser back to the seabed, and the subsea export/sales pipelines shall transport oil to an onshore facility to be treated and processed.
flexible pipe can also serve as a riser – not as a drill riser but production riser, or a riser system that stands on a riser base to connect with turrent and swivel on a fpso.
marginal field development:
there are two sorts of development for marginal fields
  • bee mode and
  • 3-1 mode
bee style is designed for satellite wells, it looks like a been that drains one well and then another, a mopu- mobile offshore production unit is needed, they told me the mopu dairy rate for chartering was 150 thousand.
3-1 mode: 1 production platform, 1 subsea cable(control system) and 1 pipeline.
i shall write in anoter essay concerning marginal field development.
Jun Wang

Random Thoughts concerning Cementing 20150802

Cementing is to seal the annular betwixt the casing pipe and the wellbore with cement slurry injected into the casing pipe,and with pressure on it, it comes up from the annular, it prevents the wellbore from collapse.

To cement is to cement with service and equipment, and the functions occur both on the surface(ground) and subsurface(downhole), any oilfield service is accomplished through the equipment, the service provider is aware of the functions of the equipment, and the equipment provider fabricates. This is also true with drilling service and drilling equipment (rig, including derrick/mast, drawworks, catwalk, hook, traveling block, doghouse etc. equipment provider fabricates and service provider operates).

This is equally true with fracturing. The fact is fracturing seems to be the enlargement of cementing as far as the surface tools and surface operation are concerned. For instance, all the functions of cementing are integrated in the cementing equipment, lets say a skid, it is integrated with blending system, manifolds etc. It is an integration in one device, but fracturing divides it, a blender/blending truck is the enlargement of the cementing skid blending system, a manifold truck is the enlargement of the manifolds in a cementing skid.

Cement equipment a trailer, truck-mounted truck or skid, consists of the following:

  • The drive/power/energy that comes from an engine
  • Blending system in a mixing tank
  • Hydraulic system (centrifuge pumps and the things in the mixing tank are hydraulically driven)
  • Lubricating system
  • Manifolds lower pressure in the mixing tank and high pressure manifolds that connect blender pump and cementing head, and cement head connects with the downhole
  • Etc.
  • And a monitor, whatever you call it, panel, console whatever, drilling rig, fracturing unit, top drive drilling system, they each has a console to monitor.


The engine provides the drive to the entire system,

  • 1, most of energy goes through the transmission and driveline to a plunger pump,
  • 2, But a small part of the energy of the engine goes to hydraulic system (blending system and centrifugal pumps), it blends with agitator, jet mixer, diffuser in a mixing tank, then the recirculating centrifugal pump circulates it, and boost centrifugal pump boosts the slurry(mixture of cement, water and additives) into the previously mentioned plunger pump which consumes most the engine energy, another centrifugal pump is called mix water, it is in conjunction with the external water source and supplies water into the blending system in mixing tank.

The cement slurry goes from the plunger to high pressure manifolds and then cementing heads into the downhole.

And 1(plunger pump, also called cement pump or big pump) plus 2(hydraulic pumps or small pumps), is nearly equivalent with the engine power because despite these two sources of energy are both supplied by the engine, there’s tiny bit additional consumption.


That I shall work on in the near future because I have got only elementary knowledge concerning what happens in the downhole, i have no idea yet the combination of the tools and the services actuated with the tools in the downhole I know cement slurry and drilling mud are separated, with pressure added on the cement slurry, it comes up from the annular betwixt the casing pipe and wellbore, and consolidates/seals the annular. I know nothing else apart from this.

Cementing doesn’t consume lots of ink, but drilling, and drilling service and equipment are expensive, and each sort of drilling (sidetracking, multilateral drilling they each consumes lots of time and ink to describe, but I have not yet mastered them)

My knowledge concerning top drive drilling system (one month training in Daqing oilfield in 2015), based on National Oilwell Varco TD Drilling System although the training is not provide by them. and subsea pipelines (flexible, based on API 17B&J, one month, training occurred in a shire yard and pipelaying vessel in Shandong in 2014)

They are very much fascinating, they both occurred on site, I shall certainly post in the near future.

Jun Wang

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