The Minghuazhen Formation in the Cangxian Uplift of Tianjin presents a unique challenge for geothermal resource development due to its sandstone reservoirs. These reservoirs are characterized by high shale content

suboptimal lithology

loosely cemented structures

and a tendency for sand flow

all of which complicate the process of reinjecting water back into the reservoir. This difficulty in reinjection poses a significant obstacle to the sustainable development of geothermal resources in the area. The existing well completion technology

which involves filter

pipe gravel filling

is beneficial in maintaining the stability of the formation and facilitating water flow. However

improvements are needed in several aspects

including drilling diameter

drilling fluid composition

drilling assembly

and well washing processes

to enhance the effectiveness of reinjection. An optimized large-diameter gravel filling well completion technology has been developed to address these issues. This technology not only preserves the original sand retention and support functions but also increases the well completion diameter

thereby enlarging the flow area of the geothermal wells. Further

by optimizing the drilling fluid formula and drilling assembly

the contamination of the reservoir is minimized. Additionally

a combined well washing technique implemented after drilling operations helps remove plugging components from the formation

aiding in unclogging the permeation channels. Three groups of reinjection tests were carried out on two reinjection wells in Minghuazhen Formation

which were constructed by the new well completion technology. The maximum reinjection rates in the tests were 32.0 m

3

/h and 58.0 m

3

/h. Compared with the reinjection wells in the same layer

the reinjection volume increased by 3.48 times and more than 2.00 times respectively

which proved that the optimized gravel filling well completion technology of large-diameter filter pipe improved the reinjection effect effectively.