Although the cause of blowout in Gulf of Mexico had been discussed in 2011 JAPT symposium, most of Japanese drilling engineers are not familiar with this incident in detail even after four years. JAPT drilling committee has decided to hold once again the symposium about this incident based on the investigation report issued by public sector agency. For making fruitful discussion with many audiences who are not familiar this incident and deep water drilling, this presentation has been prepared for introducing the outline of this incident as session 1.
It was concluded that hydrocarbon flow occurred through the 7″×9-7/8″production casing from the shoe track. A combination of casing design (long-strings or liner), cementing program, temporary abandonment plan, failure of function of float collar, contamination / channeling of cement were possible causes of hydrocarbon flow. A mitigation plan to prevent blowout is proposed and discussed in this paper.
BOP control has been worked without major trouble before this blowout incident. But finally BOP could not be shut in well even though blind shear ram has been activated when blow out occurred. Blind shear ram failed to close completely and seal the well due to elastic buckling between the upper annular and the upper VBR by pushing drill pipe by upward pressure of hydrocarbon flow. This buckling led to loss of well control. This presentation will explain the lessons and countermeasures learned from analysis of sub sea BOP system and well shut in operations of this incident.
After Macondo incident, U.S. regulatory agency had amended a wide range of rules that related to avoid this kind of incident. Particularly final rules of CFR had been modified rigorously in response to many comments received from industries. This literature introduces a typical example of changes that related to the cause of this incident.
The Miocene gas reservoirs in the volcanics of the Nishiyama Central (Chuo) oil field (NC field) and the Katagai gas field (KG field) in the Niigata district, Japan, primarily consist of altered rhyolitic rocks. This study aims to understand the porosity systematics of the altered rhyolitic rock gas reservoirs. The alteration minerals in the rhyolitic tuffs and lavas are quartz, albite, adularia, illite, and chlorite with small amounts of mixed-layer clay minerals, smectite, zeolite minerals, calcite, and pyrite. Altered rhyolitic rocks contain primary pore spaces (bubbles) and secondary pore spaces (vugs, fractures, perlitic cracks, interstitial pores, and leached pores). Interstitial and leached pores formed by hydrothermal alteration comprise the pore space of the gas reservoirs. Secondary euhedral albite crystals, which replace volcanic glass, are typically present in the interstitial pores. The crystallization of secondary euhedral albite is critical to the formation of gas reservoirs. The dissolution of secondary albite resulted in the formation of the leached pores. The presence of alteration minerals, such as adularia, illite, chlorite, mixed-layer clay minerals, and quartz in the leached pores resulted in microporosity. However, adularia and mixed-layer clay minerals are absent from the main reservoir of the KG field. The diameter of the interstitial and leached pores ranges from 0.02 to 3 μm and 2μm to 2 mm or more, respectively. Micropores less than 1 μm are predominantly present in the spaces filled with clay minerals. δ34S data for disseminated and vein-type pyrite from Miocene mudstone, rhyolitic rocks, and basalt indicate mixing of reduced sulfur from mudstone or basement rocks with magmatic sulfur. The pore characteristics, the alteration mineral assemblage, and δ34S data in the NC and KG fields suggest that the interstitial pores formed early and the leached pores owing to hydrothermal alteration by seawater followed. Subsequently, alteration minerals filled the micropores during diagenesis.
Temporary abandonment operations that led to the oil spill incident in Gulf of Mexico were analyzed focusing on temporary abandonment procedures and actual operations from the negative pressure test to blowout occurrence. Temporary abandonment plan went through remarkable transitions from original plan to actual plan. Especially cement in shoe track was the only active barrier when negative pressure test was conducted under considerable different risk factors associated with cement job. The plan was changed to efficiently perform temporary abandonment operations since there were delay of the process and cost increase. In this circumstance, the negative pressure test was done and all members on site believed that cement barrier has been successfully tested regardless of presence of strange pressure behavior due to overreliance on leader's judgment. During displacement SOBM (Synthetic Oil Base Mud) with sea water in marine riser, blowout occurred. Although there was a lot of opportunity to detect the kick during this operation, nobody could stop operation until gas came in marine riser.
A unique method for quantifying anisotropic fabric in rocks is reviewed and its value for reconstruction of the preferred direction of pore fluid flow is reassessed. Magnetic techniques that use anisotropy of magnetic susceptibility act as a proxy of permeability anisotropy of reservoir, when it is applied on samples impregnated with liquid containing suspension of magnetic powder. The authors also present preliminary results of their experiments, which evaluated fracture networks developed in tight turbidite sandstones in central Hokkaido. Rock magnetic analyses and micro-focus density imaging have shown a substantial change in pore fabric reflecting inhomogeneous impregnation of magnetic fluid within sample rocks.