How to make rational use of water resources in oil gas field development

Coalbed methane (CBM), shale gas tight gas reservoirs are often superimposed in the area along the Yellow River of Shanxi Province. As a pilot province for the comprehensive reform of the energy revolution, the state authorized Shanxi to take the lead in the pilot in the whole country, endowing the above-mentioned "three gas" mining rights to the same subject, opening the door to the construction of a national unconventional gas base.

"As an important unconventional oil gas resource, tight gas reservoirs have become the focus of exploration development at home abroad in recent years, also become the main force to promote unconventional gas storage production in Shanxi Province. In the face of the disposal of high-salt drainage water in tight gas development, there is an urgent need to strengthen theoretical technical research on drainage mining water reinjection, accelerate the formulation of relevant standards norms, promote pilot demonstration of reinjection projects." Xiao Lei, director of the economic operation regulation department of the Shanxi Development Reform Commission, said this at a recent seminar on reinjection disposal technology of drainage water in tight gas development in Shanxi Province.

According to several industry insiders, with the continuous intensification of tight gas exploration development, the water discharged during the development process has risen sharply, the traditional treatment disposal methods can no longer meet the development needs. However, due to the chemical characteristics of high chlorine high salt in the drainage water produced by the development of tight gas, it is difficult to deal with high cost, which has become the main factor restricting the increase of tight gas storage production in Shanxi Province. In this context, reinjection formation, as a kind of drainage water disposal method widely adopted in domestic foreign oil gas industry, has attracted widespread attention of tight gas development enterprises in Shanxi Province.

In fact, only in the field of tight gas development, but also how to reduce water consumption sewage treatment, has become a major issue facing China's oil gas industry.

The "water problem" restricts development

"As a pilot of comprehensive reform of energy revolution, Shanxi Province has great potential of unconventional gas resources. It should continue to promote the reform of various management measures to promote the steady growth of unconventional gas production achieve the goal of increasing reserves production." "Said Lian Bipeng, director of the Natural Resources Department of Shanxi Province.

Tight gas, as the dominant mineral resources along the Yellow River in Shanxi Province on the eastern edge of Ordos Basin, is a key industry to be developed in the process of energy revolution in the province. "In recent years, with the increasing intensity of tight gas exploration development in Shanxi Province, the treatment disposal of high-salt drainage water generated in the process of tight gas development has seriously restricted the development of the industry. The reinjection project should focus on the pollution effects of regional fault structures borehole intersections on the upper aquifers with water supply significance." Shanxi CBM Industry Association President Ding Min pointed out.

The Notice on Further Strengthening the Management of Environmental Impact Assessment in the Oil Gas Industry, published by the Ministry of Ecology Environment in December 2019, stated that " wastewater reinjection is involved, it should generally be reinjected into existing oil gas reservoirs depleted abandoned oil gas reservoirs". According to the requirement of "injection in the same layer", the drainage water produced in the process of gas production is injected back into the gas producing layer again. Under the condition that the gas producing layer has been disturbed by fracturing, the drainage water produced in the process of gas production is injected back into the layer again, which can reduce the impact of injection on underground environment to a large extent.

"It is of great significance for the sustainable development of the tight gas development industry in Shanxi Province to study demonstrate the drainage mining water reinjection technology, orderly promote the implementation of the drainage mining water reinjection project, strengthen the environmental risk management of the drainage mining water reinjection." Ding Min further said.

A number of industry insiders suggest that environmental risks of the project should be effectively controlled during the reinjection process. According to the principle of "one well, one policy", targeted environmental protection target identification should be carried out, monitoring of the reinjection process should be strengthened, environmental risk prevention control measures should be formulated, with the focus on preventing the impact on drinking water sources. Both conventional unconventional oil gas development should focus on the "water issue."

Lack of systematic research

Data show that only about 9% of the oil gas industry's development projects involve drainage water reinjection projects.

Fan Zhenzhen, a senior engineer at the Environmental Engineering Assessment Center of the Ministry of Ecology Environment, said that the current EIA work in the oil gas industry has problems such as small investment short cycle in the management of a single well, but large amount of review, large amount of management low efficiency. In addition, exploration development only pay attention to the ground work such as well site, systematic research is enough, the impact analysis on the ecological environment groundwater environment of the whole region is weak. In order to promote the coordination between oil gas development ecological environment protection, to realize the green development of the industry, it is urgent to introduce EIA management policies covering both conventional unconventional oil gas.

It is worth noting that the reinjection of drainage mining water in Shanxi Province is still in its initial stage, with weak basic research in relevant fields, lack of standards regulations, absence of policies measures. Technical supervision policies regulations at the national level are in urgent need of strengthening.

Experts at the meeting said that relevant studies should be carried out based on foreign experience comprehensive evaluation of environmental effects, the contents of layer selection well selection, wellbore safety, reinjection parameters, monitoring management abandonment plan should be standardized in the process of oil gas exploitation, the technical requirements of wellbore integrity wellbore structure should be clarified, so as to provide a basis for relevant legislation.

Policy constraints are absent

At present, due to the lack of relevant policies, norms legal constraints, it is urgent to take practical measures to prevent control groundwater pollution strictly prohibit the reinjection of waste water unrelated to the production of oil gas fields.

Fan ZhenZhen pointed out that the EIA documents of construction projects should disclose information on the toxic, hazardous heavy metal components in drilling fracturing fluids, strengthen the research on the reinjection of produced water other sewage, with the focus on the rationality of the well location, the effectiveness of process control the systematic risk prevention control.

"Post-hoc supervision should be strengthened. Oil gas exploitation enterprises shall report the implementation changes of projects the ecological environmental protection to the ecological environmental departments jurisdiction annually. Ecological environmental departments at all levels should adopt a 'double random, public' approach to strengthen supervision, strengthen technical checks in the quality check of EIA documents, punish problems found in accordance with the law regulations." Fan Zhenzhen further pointed out.

A number of industry insiders said that research on multi-level utilization technology of oilfield sewage resources should be carried out in depth, a complete set of multi-level recycling technology system for heat, water chemical materials sewage should be formed, so as to realize the sustainable green development of turning waste into treasure. At the same time, we should control pollution the source to reduce water consumption sewage treatment costs.

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Source: International Petroleum Network