Use of Downhole Production/Reinjection for Zero-Emission Well Testing: Challenges and Rewards

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn recent years, HSE concerns have been a driving force pushing towards emission-free well testing. Several methods have been proposed in order to attain that objective, the two most known being closed-chamber testing and downhole production/reinjection. With closed-chamber testing being of limited interest because of the reduced radius of investigation it offers, and harmonic testing being impractical due to time requirements, downhole production/reinjection appears as the only way of fully replacing conventional well testing.Planning such a test requires greater care than for a conventional test because the selection of an adequate injection interval is of major importance to the success of such an operation. The injected fluids must be contained within the disposal zone so as to avoid surface leakage but also so that the test data are not affected by an interference effect due to the injection process. There is also a great concern regarding the quality of the data because of hard downhole conditions. But if these challenges can be overcome, downhole production/reinjection can provide the same information as a conventional well test but with improved safety, no direct emission of pollutants and at reduced cost and test duration.

Green Methodologies to Test Hydrocarbon Reservoirs

“…A valid contribution to the review and discussion of technologies such as wireline formation tests, closed chamber tests, production/reinjection tests and injection tests as viable alternatives to conventional well testing can be found in the technical literature (Coelho et al, 2005;Woie et al, 2000;El-Khazindar et al, 2002;Hollaender et al, 2002;Banerjee et al, 1998;Beretta et al, 2006;2007).…”

“…Some authors report that the CCT technique is a valid alternative to conventional well testing because it has a lot of advantages such as: It offers great security and safety; the test provides formation permeability, reservoir pressure, skin and, depending on the volume flowed, a fluid sample; it provides a basis for rate determination, particularly for gas wells; it appears particularly suited to testing low permeability gas wells; it is a very simple methodology and it can be performed with existing equipment that requires limited extra hardware; a particular feature of CCT is that the test may be switched to a conventional test, i.e., the surface valve may be opened at any point during flow periods (Hollaender et al, 2002;Soliman et al, 2004;. However, CCT's have a lot of disadvantages: There is no assurance about the quality of the sampling, as drilling and completion fluids might be produced rather than reservoir fluids; only one test is possible and once the wellbore is filled no other test can be done; the fact that there is only a limited volume to be produced during the test has a large impact on the radius of investigation of such a test; depths of investigation from CCT are generally in one hundred of feet which makes them inapplicable for boundary or barrier detection; complex wellbore dynamics affects pressure response; the well may not be 'clean' prior to the test and hence the results may be distorted.…”

“…Furthermore, not only do atmospheric emissions have a damaging impact on the environment, but they also impose an economic impact: the cost of the oil and gas flared and the cost of the equipment used during the flaring operations as performing a well test typically costs several million dollars mostly due to required rig time and loss of production. Because of the high costs involved in well test operations, especially in offshore exploration wells, the test type must be carefully chosen and properly designed in order to meet its required objectives at the lowest cost (Hollaender et al, 2002).…”

Environmental Sustainability of Oil Industry

“…All the test parameters, such as flow rates, pressure and temperature data are monitored and controlled from the surface. This methodology permits to test both production and injection layers and to collect fluid samples (Woie et al, 2000;Hollaender et al, 2002).…”

“…Furthermore, the environmental and safety issues are significantly reduced because no hydrocarbons flow to surface during the test (Woie et al, 2000;Hollaender et al, 2002). Despite the environmental and economic advantages, the applicability of the methodology has to be carefully evaluated for each case, since a number of technical disadvantages could occur.…”