Cement Failure Probability under HPHT Conditions Supported by Long Term Lab Studies and Field Cases

Abstract

Cement durability is very important to maintain proper well isolation and stability under HPHT conditions. In the process of well completion and production, pressure decline and temperature variation with time can contribute to cement failure and wellbore stability issues. However, there is no available investigation in the durability and comparison of different types of cement at higher temperature and at different operational scenarios. Three different types of cement (72 pcf, 101 pcf and 118 pcf) commonly used in the Middle East were cured and tested at 300°F in the study. The tests included one year mechanical properties measurement such as compressive strength development, Young's modulus and Poisson's ratio. Finite element method was used to analyze the failure probability of HPHT wells over with time. At the variation of bottom hole pressure and temperature, the casing, cement, and formation system failure probability was studied for these types of cement. The results show that the pressure variation has more effect on the wellbore stability than the temperature variation for HPHT wells. Low density cement can improve the wellbore stability issues due to the cement elastic behavior. This paper introduces the operational envelope for every type of cement investigated in order to achieve successful operations based on field conditions. Field cases were discussed to validate the results of this investigation.

Integrity Evaluation of Cement Ring during Fracturing and Flowback of Horizontal Well in Jimsar Shale Oil

“…Since the mechanical model of casing/cement ring/ formation assembly is axisymmetric, the physical and mechanical model is a plane strain problem in the polar coordinate system (Figure 1). The relevant variables include radial displacement, radial stress, circumferential stress, and shear stress [12][13][14][15][16][17]. Among them, the inner surface of the casing bears the radial stress caused by the increase of wellbore temperature and pressure caused by wellbore fluid.…”

Study on sealing integrity of cement sheath in ultra deep well reservoir reconstruction

“…The integrity of the cement sheath is determined by the intersection of the load‐bearing characteristic curves of each part, avoiding the complicated problem of directly calculating the failure of the first and second interfaces 15 . Heathman found that changes in wellbore pressure can cause the cement sheath to fail 16 . Subsequently, they developed a personalized design method for cement slurry systems to address this issue and applied it to cementing a high‐temperature and high‐pressure gas well in East Texas 17 .…”

“…15 Heathman found that changes in wellbore pressure can cause the cement sheath to fail. 16 Subsequently, they developed a personalized design method for cement slurry systems to address this issue and applied it to cementing a hightemperature and high-pressure gas well in East Texas. 17 Z. Shen and Beck developed a 3D finite element model considering five layers of strata to simulate the mechanical response of casing and cement sheath in nonuniform layers with interlayers.…”

Development and application of on-line calibration device for water injection flowmeter

“…In the absence of an alternative flowmeter, a calibration requires at least two service visits to the site, and the water injection has to be stopped which will affect production. In the actual water injection process, the water injection flowmeter can not be calibrated twice a year that seriously affects the normal water injection metering and the fine water injection development [6][7][8][9]. Therefore, combined with the actual production situation, the paper studies the on-line calibration technology for the field water injection flowmeter that can meet the calibration technical requirements and operation management specifications.…”