Research and Development
Future Well Control AS was founded in 2015 in order to finance a PhD project carried out by Dag Vavik. The R&D work was financed by Future Well Control with financial support from Lundin Norway, Innovation Noway, Forskningsmobilisering Agder, RFF Agder and The Research Counsil of Norway. The research project was carried out in close collaboration with NTNU and SINTEF.
Future Well Control patented and innovative solutions are based on new knowledge about the root cause of the challenges that may occur during drilling and completion. Challenges caused by Swap Out, Gas Solubility and Thermal Effects requires new solutions. Although these phenomenon are not new knowledge as such, the implications are often neglected or poorly understood. You may read more about the PhD work and read a summary of the PhD thesis by clicking on the link below: Implications of Gas Hydrates in Drilling and Completion - A Scientific Root Cause Analysis of the Deepwater Horizon Disaster.
If you want an abstract of the major findings in our research, you may read more about Thermal Effects, Gas Solubility and Swap Out below.
Dag Vavik, PhD.
Thermal Effects & Gas Solubility
Figure A was presented at the IADC Well Control Conference in 2022 and shows how thermal effects and compressibility of SOBM affect the active pit volume. Simulation shows a period of 72 hours static condition of the Macondo well. Shortly after circulation stops you will see a pit gain due to SOBM compressibility and thermal effects of about 0.5 m3 (3.1 bbls).
In the next 24 hours the thermal effects will result in a "loss" of fluid or more correctly a reduction in the active volume of about 4 m3 (25 bbls). This means that you may take a gas kick of about 50 bbls without any observed gain at the surface, since gas in solution will only take up about 50% of the volume of free gas.
Gas Diffusion & Gas Hydrates
When gas influx is dissolved in SOBM it will after some time diffuse to the wellhead and riser. In a similar but different way free gas will migrate in WBM. In the wellhead and riser area the mud is colder and temperature will also rapidly decrease after circulation stops, see figure B. The hydrate formation temperature is depending on salt content and on pressure (water depth and mud weight). In deep water it will only be matter of time to reach conditions when gas hydrates may form. When gas hydrates is formed, gas is "consumed" and the fluid volume is reduced even more.
In a static riser, dissolved gas that is not trapped as hydrates will typically diffuse higher up in the riser and "boil out" of the SOBM when pressure is sufficiently low. Free gas may "boil" out in an open riser or collect in top of the booster line, without any flow in the flow line.
Erratic Flow Out & Swap Out
Figure C was presented at the IADC Well Control Conference in 2020 and shows simulated and real-time values from the last 3 hours of the cement job in the Macondo well. The erratic but considerable less flow out compared to pumped flow in, may have been to dissolved gas in the riser and gas boiling out and leaving the riser before the fluid is measured in the return flow meter. Event (4) and (7) may have started with a partial loss of fluid due to high pressure fluctuation followed by a gas kick. When fluid is partly or totally lost in a loss zone and gas is entering the well from a high pressure zone simultaneously, we may call this for a swap out event. Gas kick caused by loss (swap out) will not necessarily be detected with a gain at surface, see event (4). In a similar way total loss of fluid will not necessarily be detected with a total loss at surface, if partly replaced with gas influx (swap out), see event (7).
Rapid gas expansion
Figure D is taken from the PhD thesis, see Figure 7.1, page 145. The drilling crew probably made two different attempts to bleed down abnormal pressure, see event (13) and (14). Rapid gas expansion in combination with blocked or restricted outlets may lead to high pressure in the riser. Flow recorded by the two different flow transmitters as well as flow recorded in the trip tank and witness statement shows that riser unloading started in the last 2 to 3 minutes. During this period the diverter housing and divert line was probably restricted with gas hydrates, resulting in high recorded pressure on the standpipe, see event (16).
You may download a complete PDF of the complete PhD Thesis from NTNU by klikking on the link