New formula for acid fracturing in low permeability gas reservoirs: Experimental study and field application

Jiang

Energy Exploration & Exploitation

et al. 2012

The Siegenian Formation reservoir is a tight sandstone reservoir with relatively poor porosity and low permeability. In this paper, the reservoir characteristics and its main controlling factors of the Siegenian Formation in X block have been studied based on cores, well-logs, and formation test data including the thin sections and cast thin sections, observation of scanning electron microscope, pressured-mercury testing and X-ray diffraction analysis of clay minerals. During deposition of the Siegenian Formation, the depositional environment was predominated by lower shoreface, middle shoreface and offshore. The fine sandstone and siltstone formed in the middle shoreface environment is the main reservoir of the Siegenian Formation in X block. Six pore types including primary intergranular pores, intragranular dissolved pores, intergranular dissolved pores, moldic pores, cement dissolved pores and microfractures are identified in the Siegenian Formation reservoir. The quartz intergranular dissolved pores and the quartz overgrowth cement dissolved pores are found for the first time in this area. The secondary dissolution pore is the main pore type in X block. The pore throat has a small radius, poor connectivity and the pore structure parameters are poor. Combined with the petrophysical property and capillary pressure curves, the reservoir of the research area is divided into three types: mesopore-ultra low permeability reservoir (type I), low-middle porosityultra low permeability reservoir (type II) and low porosity-ultra low permeability reservoir (type III). Type II is the main reservoir in this area. The sedimentary environment, tectonism and diagenesis are the main controlling factors. Diagenesis is the most important controlling factor in this area. Diagenesis may play a catalytic role or may play a negative role on damage in the reservoir pore evolution. The compaction, pressure solution, cementation, replacement and cementation are the main diagenesis types which reduce the pore volume during the reservoir pore evolution. The dissolution including acidic dissolution and alkaline dissolution are the main diagenesis types which produce extra pore volume during the reservoir pore evolution. This study of the reservoir will guide the future exploration of this area.

Section: The Diagenesis Of Producing the Poresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reservoir Characteristics and its Main Controlling Factors of the Siegenian Formation of Devonian in X Block, Algeria

Jiang

Energy Exploration & Exploitation

et al. 2012

“…Compared with the conventional natural gas reservoirs, coalbed methane (CBM) reservoirs feature with extremely low porosity and permeability, which makes it hard for the exploitation of CBM 1 . Various hydraulic fracturing technologies have been used for an enhanced recovery of oil and gas 2‐4 . The refracturing technology has been verified to be an effective way to improve the performance of hydraulic fractured wells 5,6 .…”

Section: Introductionmentioning

confidence: 99%

Refracturing field tests for enhanced coalbed methane production with gas wettability alteration

Lin

Zhao

et al. 2021

Int J Energy Res

Summary Gas wettability alteration (GWA) technology has been used for better methane drainage underground. Our previous field tests of underground fracturing demonstrated a large increase in coalbed methane (CBM) production compared with those in the boreholes fractured without GWA treatments. However, the general drainage rate of each fracturing borehole with GWA treatment is not high enough because no proppant was used in the underground fracturing. To this end, field tests of surface refracturing in two CBM wells (Wells A‐2 and 4) were conducted with an innovative fracturing measure with GWA treatments and elongated coal‐like proppants in XJ coal mine, Yangquan, China. The water and CBM production with the novel and the conventional fracturing technologies were compared and analyzed. The field test results showed that the CBM production with the novel refracturing technologies (29 697 and 26 844 m3 for Wells XJ‐2 and 4) is greater than those with conventional refracturing (22 746 m3 for Well XJ‐6) and initial‐fracturing (25 297.4 and 2847.2 m3 for Wells XJ‐2 and 4). The significant increase in CBM production demonstrates that the novel fracturing technology could be applied for enhanced CBM production.

“…In tight gas reservoirs, it is usually necessary to conduct acid-fracturing to improve gas production. The problem is the low liquid return rate after stimulation of acid fracturing which may cause serious secondary formation damage 21 . If the wettability of rock in tight gas reservoirs were changed from water wetness to gas wetness, the liquid return rate might be increased and therefore the gas production might be improved.…”

Section: Introductionmentioning

confidence: 99%

Production Enhancement in Gas-Condensate Reservoirs by Altering Wettability to Gas Wetness: Field Application

Liu²

2008

All Days

Liquid condensation in the rock near wellbore may kill gas production in gas-condensate reservoirs when pressure drops lower than the dew point. It has been proved both theoretically and experimentally that gas production in gas-condensate reservoirs could be improved by altering wettability of rock near wellbore from liquid wetness to gas wetness. However, to our best knowledge, few field applications have been reported. In this study, a pilot test was designed based on experimental results measured in the rock sampled from the target gas-condensate reservoir. The gas-condensate field, located in central China, was a high temperature and low permeability reservoir with a permeability of less than 0.1 md. About 30,000 litters of chemical solution were injected into a well in the gas-condensate field. The test results showed that the gas production of the well was increased significantly.