On the assessment of the amount of crude oil spilled into the Black Sea

On February 25, 2022, the Caspian Pipeline Consortium sent to the head of the Federal Service for Supervision of Natural Resources (Rosprirodnadzor, RPN) an application containing an estimate of the volume of oil leakage from the single point mooring (SPM-1) on August 07, 2021, made using a hydraulic model with the certified software. This estimate was made in accordance with the agreements reached at a meeting on January 25, 2021, which was chaired by the head of Rosprirodnadzor S.G. Radionova.

It is encouraging that the head of the federal agency praised the competence of CPC specialists to reliably estimate the volume of oil released as a value that significantly affects the calculation of the amount of damage.

Head of Rosprirodnadzor - RBC:"To kill business there is no sense"

However, in violation of the established dialogue and before receiving calculations from the company, Rosprirodnadzor filed a lawsuit in the Arbitration Court of Krasnodar Krai to recover damages from CPC-R, recalculating the amount significantly higher than previously stated in the department's calculations.

As a reminder, during CPC's loading operations through SPM-1 to the Minerva Symphony tanker, there was a sudden failure of a flexible expansion joint on the internal ND600 loading line, which resulted in oil leakage from the damaged expansion joint with varying intensity for about 17 minutes. The leakage time has been fixed by Rosprirodnadzor.

For reference, CPC provides photographs illustrating the challenging nature of the expansion joint damage. As shown in the photo, the tightness of part of the inner and outer jacket of the expansion join has been preserved, which indicates that the flow was only through a limited area of the hole with additional hydraulic resistance, and not in the conditions of a guillotine rupture of the oil pipeline.

CPC Marine Terminal (MT) is a sophisticated technological facility consisting of the following main elements: Tank farm (TF), DN1400 inter-site process pipeline, shore facilities (SF) with pressure control units and custody transfer meters, DN1050 subsea process pipelines and single point moorings (SPM) with subsea and floating hoses.

The oil loading technology is based on the gravity effect due to the difference of geodetic marks of the Tank Farm and the shore facilities. Due to the specified difference in hydrostatic pressure oil from the TF tanks flows by gravity through the DN1400 inter-site pipeline to the SF and then through the DN1050 subsea pipelines to the SPM, from where it is transported by two DN600 floating loading hoses to the tanker tanks. The schematic diagram of oil loading on the CPC MT is shown below.

 

In order to make a qualitative assessment of the volume of oil leakage through the damage in the flexible SPM-1 joint, it was proposed to apply a hydraulic model of the loading scheme using the certified licensed software “Hydraulic system” version 4.4 R1 by NTP TRUBOPROVOD. This program allows you to set the exact geometric and element model of technological networks of any complexity with the possibility of hydraulic calculations.

As an example below, the working window of the program with a model of the process piping of SPM-1, including all elements of the piping with places of hydraulic resistance.

 

 Circumstances of the leakage

Based on the available nature of the pressure trends in the inner and outer loading lines, we can conclude that the damage to the flexible joint in the inner loading line developed in two stages.

Since after the destruction of part of the metal cord and the outer rubber layer of the damaged expansion joint, the pressure in both loading lines remained excessive and at a fairly moderate level, we can conclude that the nature of the damage was not a through hole, but a hole with local resistance (part of the inner and outer rubber layers, as well as sections of the metal cord), affecting the intensity of oil flow.

Thus, the damage to the flexible joint was not guillotine (used in the RPN calculation method), as there was no complete rupture across its entire surface, which is confirmed by photographs of the damage and the presence of excess pressure in the flexible joint area during the entire time of active flow.

It is also important to note that the elevation points of the beginning of the subsea pipeline (zero end) and the end of the subsea pipeline including subsea hoses (SPM-1 buoy) are almost the same and are much higher than the part of the pipeline laid on the seabed. Because of this, after the active phase of oil flowing out of the damaged expansion joint at SPM-1, the entire subsea pipeline, including the onshore section and subsea hoses, remained completely filled with oil.

Basic conditions for performing leakage calculations

To carry out a series of calculations to simulate the volume of leakage through the fault in the expansion joint using the “Hydraulic system” software, the flow process was divided into elementary time intervals, within which the averaged parameters of the flow could be considered constant. In addition, the following circumstances must be taken into account in the calculations:

• The readings of the pressure sensors at the SPM and the LACT flow meter have different measurement resolution, in this connection the readings of these sensors at a particular time unit may not reflect the actual situation of the ratio of pressures and oil flow through the LACT unit;
• After the expansion joint was damaged, a transient process began, accompanied by waves of increased and decreased pressure and flow, which at different intervals were in the area of pressure sensors and flow meters of the LACT, which also influenced the actual distribution of flow and pressure parameters;
• After closing block valves at pressure control stations XV-0006A/C/E at 17:01:01, the residual emptying of part of the onshore pipeline began, and then valves at pig L/R XV-0040 and ESV-005 emergency valve at the shoreline were closed.

Basic results of the performed leakage calculations

As a result of the use of a certified engineering software for building a qualitative hydraulic model of the oil loading scheme through SPM-1 and the subsequent series of calculations on the oil leakage from the damaged expansion joint (20 basic calculations were carried out), the total volume of oil spill during the oil leakage period was - 89.1 m3 or 69.1 tons.

The specified volume of the leakage is also confirmed by the calculations of the Institute of Space Research of the Russian Academy of Sciences during the international conference "Modern problems of remote sensing of the Earth from Space". (Moscow, November 15-19, 2021, slide 16).

In addition, some subject matter experts were also able to calculate the mathematical task, earlier proposed by CPC, the solution of which proves from the standpoint of physics that the volume more than specified could not get into the Black Sea under similar flow conditions.

For information:

The CPC Pipeline System is one of CIS largest energy investment projects that involves foreign capital. The length of the Tengiz – Novorossiysk pipeline is 1,511 km. This route moves over two thirds of all Kazakhstan export oil along with crude from Russian fields including those in the Caspian region. CPC Marine Terminal is equipped with three Single Point Moorings (SPM), allowing tankers to be loaded safely at significant distance offshore, including in poor weather conditions

CPC Shareholders: Federal Agency for State Property Management represented by Transneft (trustee) – 24%, CPC Company – 7%, KazMunayGas – 19%; Kazakhstan Pipeline Ventures LLC – 1.75%, Chevron Caspian Pipeline Consortium Company – 15%, LUKARCO B.V. - 12.5%, Mobil Caspian Pipeline Company - 7.5%, Rosneft-Shell Caspian Ventures Limited - 7.5%, BG Overseas Holding Limited - 2%, Eni International N.A. N.V. - 2%, and Oryx Caspian Pipeline LLC – 1.75%.