Methane emissions from oil and gas production and transport are under intense scrutiny. A number of states have implemented, or are in the process of implementing regulations, and the Obama administration is undertaking a similar program. The California Air Resources Board (CARB) recently proposed regulations for crude oil and natural gas operating facilities. These proposed rules cover the entire cycle from separator and tank systems to circulation tanks with some exemptions based on tank sizing/flow rate and frequency of use. Leak detection and repair (LDAR) will include reciprocating and centrifugal natural gas compressors, and pneumatic devices and pumps, again with some exemptions. Annual flash analysis testing is required in accordance with the CARB Test Procedure in the regulations with strict record-keeping and reporting requirements. Liquids unloading operations will also require gas collection/measurement to meet the rule. California, under the proposed regulations, will require exploration and production operators to control emissions by 2018 with a phase-in allowance for existing systems by 2019.
LDAR requirements include daily (24-hour cycle) audio-visual inspections with measurement using Method 21 where leaks are detected and quarterly testing using this method of all components. Optical gas imaging is also an optional screening tool in place of the audio-visual approach.
The proposed rule includes a test procedure for determining the annual flash emission rate of methane from crude oil, condensate, and produced water. These samples must be collected under pressure either via a double valve cylinder, or by a pressurized piston-equipped cylinder. American Standards and Testing Materials (ASTM), US Environmental Protection Agency (US EPA), and Gas Processor Association (GPA) methods were used as the basis for the required laboratory analysis. Biases and interference issues are possible, and both the collection steps and the laboratory analyses should be carefully planned and then audited early, and perhaps routinely, in your operation to ensure that, “… records [shall] provide direct evidence and support necessary for technical interpretations, judgments, and discussions concerning project activities …” Environmental Standards routinely performs field sampling and laboratory auditing to assess compliance with the methods included in these proposed CARB regulations.
Methane emission measurements also continue to be an area of significant research with new technologies under development using laser spectroscopy/spectrometry and on-chip sensors that can be distributed across a facility site network. Management of the huge volumes of data and computational analysis will be critical for operational analysis and decision making.