Zheng R.,Chengdu University of Technology |
Pan Y.,Chengdu University of Technology |
Pan Y.,Sichuan Nuclear Geology Institute |
Zhao C.,Chengdu University of Technology |
And 3 more authors.
Journal of Earth Science | Year: 2013
Based on the detailed research on petrologic and geochemical characteristics of deposition and diagenesis of Oxfordian carbonate rocks in Amu Darya Basin, Turkmenistan, carbon and oxygen isotopes were analyzed. The results show that the paleoenvironmental evolution reflected by the samples with well-preserved original carbon isotopes coincides with the carbon-isotope stratigraphic curve and is almost consistent with the global sea-level curve, the Mid-Oxfordian wide transgression, and the positive carbon-isotope excursion event. The Mid-Oxfordian continuing transgression not only laid the foundation for the development of the Oxfordian reef and shoal reservoirs in Amu Darya Basin but also provided an example for the Oxfordian global transgression and the resulting development of reefs and banks and high-speed organic carbon burial events. The response of oxygen isotopes in diagenetic environment showed that micrite limestones and granular limestones underwent weak diagenetic alteration, and the samples largely retained the original seawater features. Dolomitization and the precipitation of hydrothermal calcites filling solution vugs and fractures before hydrocarbon accumulation occurred in a closed diagenetic environment where the main controlling factor is the temperature, and the diagenetic fluids were from the deep hot brine. The chalkification of the limestones after hydrocarbon accumulation occurred in the oilfield water systems. © 2013 China University of Geosciences and Springer-Verlag Berlin Heidelberg.
Cheng W.,CNPC International Turkmenistan |
Wang L.,China National Petroleum Corporation |
Li G.,China National Petroleum Corporation |
Wang Y.,CNPC International Turkmenistan |
Ding Q.,China National Petroleum Corporation
Natural Gas Industry | Year: 2014
The high temperature, high pressure and sour gas fields on the Right Bank of the Amu Darya River, Turkmenistan, are featured by complex geological structures and low permeability. Natural gas there generally contains corrosive gases such as H2S, CO2. Many accidents occur in block testing, for example, unsealed downhole test string, corrosion and damage to tubings and pressure-resulted leakage, thus affecting the construction schedule and the safety of personnel and equipment. In order to prevent these accidents, from the perspective of process and safety, following the principle of "being simple and practical", we analyzed the application characteristics and technology of the existing four DST string structures to work out an optimal design of a drill stem test (DST) string (i. e., perforation - testing - acidification - testing - bullheading string) for this block. The string is composed of a TCP string + a RTTS packer + a safety joint + a RD circulation valve + a RD safety circulation valve + an OMNI multifunction circulation valve (no ball) + a marker sub + a christmas tree. If the well is put into production after testing, a permanent bayonet-tube packer can be used to replace RTTS packer, converting to perforation - acidification - testing - completion string. The optimized string design has been successfully applied to the testing operations of five wells, providing a technical support for guiding the testing design of high temperature, high pressure and sour wells, effectively preventing incidents, and accurately acquiring all formation data.
Wang H.,Petrochina |
Zhang P.,CNPC International TURKMENISTAN |
Cheng Y.,Southwest Petroleum University |
Leng Y.,CNPC International TURKMENISTAN |
And 7 more authors.
Shiyou Kantan Yu Kaifa/Petroleum Exploration and Development | Year: 2014
In view of the long pressure stabilization time of low permeability gas reservoirs, the traditional backpressure test was modified based on the idea of isochronal test in order to evaluate gas well productivity accurately. Firstly, carry out continuous well startup using 3-4 incremental working systems at the same time interval without the bottom-hole flowing pressure reaching stability; then carry out a prolonged test using a reasonable working system which requires both the bottom-hole flowing pressure and the production reaching stability; finally shut in the well to allow the pressure recover to formation pressure. If the isochronal test productivity calculation method is borrowed for the modified backpressure test, the drawdown pressure will be overestimated, and calculated productivity will be underestimated. The process conversion-flowing pressure correction was used to convert the test process into an isochronal test process, and the bottom-hole flowing pressure correction equation was deduced based on pressure superposition principle to solve the productivity calculation problem with this method. The example indicates that the modified backpressure test method can not only shorten the test time significantly and avoid frequent well startup and shut-in, but also can ensure the accuracy of productivity calculation.