| Title | Laboratory Study on Formation Damage in Geothermal Reservoirs Due to Fines Migration |
|---|---|
| Authors | Alexander BADALYAN, Themis CARAGEORGOS, Zhenjiang YOU, Ulrike SCHACHT, Pavel BEDRIKOVETSKY, Martin HAND, Chris MATTHEWS |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | geothermal well, formation damage, rock fragments, fines migration |
| Abstract | Here we present a new method to assess formation damage in geothermal reservoirs. It is long known that formation damage is caused by mobilisation, migration and straining of natural reservoir fines. Thus the laboratory methodology developed and presented here aims to determine the permeability decline from rock fragments. It includes: development of a composite porous medium consisting of borosilicate glass beads and sandstone fragments; mobilisation of fines from fragments by alternation of velocity and ionic strength of water flowing through this porous medium; identification of minerals in collected fines; calculation of the total potentials of interaction between fines and sandstone matrix and their effect on fines mobilisation and formation damage. Velocity-induced fines migration is responsible for a non-significant reduction of rock permeability leading to initial formation damage. Following low-ionic strength water injection increases electrostatic repulsion force between clay particles and sand surface, further mobilizes particle resulting in formation damage. Mobilised fines with mixed-layer illite/chlorite mineralogy are responsible for rock permeability reduction due to pore-throats clogging. Fines migration is one of the most widely spread physics mechanisms of formation damage in oil and gas wells. Numerous recent publications report well impairment by fines migration in geothermal fields. Estimation and prediction of well formation damage is carried out by evaluation of fines removal capacity and fines migration in rocks from the well for which cores and fragments are available. The proposed method is applied to assess possible formation damage in the geothermal reservoir using its rock fragments in the absence of cores. Appreciable residual permeabilities for studied rock fragments at ionic strength of reservoir water indicate that the studied geothermal well is probably capable of producing commercial quantities of geothermal fluids. |